Urban Water Management and Public Acceptance of Rainwater Harvesting Systems: Insights from Young and Educated Respondents in Muslim Communities

Abstract

As water scarcity and environmental sustainability become increasingly critical global concerns, there is a growing need to identify alternative water resources. This study investigates public acceptance of Rainwater Harvesting (RWH) systems in Brunei Darussalam for non-potable uses and ablution purposes. Using an extended Technology Acceptance Model (TAM) framework, the research evaluates key factors influencing public perceptions, including Perceived Ease of Use (PEU), Perceived Usefulness (PU), Attitude Towards Use (ATU), Intentions to Use (ITU), and external factors such as Perceived Cost (PC), Subjective Knowledge (SK), and Technical Requirements (TR). Survey data were analyzed through regression techniques to assess these relationships. The results validate the TAM framework for understanding acceptance of RWH systems and highlight strong positive relationships between PEU, PU, and ATU, with ATU emerging as the strongest predictor of behavioral intentions (ITU). External factors like PC and TR were identified as barriers to adoption, emphasizing the need for financial incentives and technical support. Additionally, subjective knowledge was found to positively influence PU and ITU, underscoring the importance of public awareness campaigns. While concerns about the safety and quality of recycled rainwater were present, they were not significant deterrents to acceptance. The findings also reveal broad support for initiatives such as education, technical guidance, and maintenance services to enhance adoption. Muslim respondents expressed positive attitudes toward using rainwater for ablution, aligning with religious principles of water conservation. This study provides valuable insights for policymakers and relevant agencies to promote RWH systems as a sustainable water management solution, aligning with global Sustainable Development Goals (SDGs) 6 (Clean Water and Sanitation), 12 (Responsible Consumption and Production), and 13 (Climate Action).

1. Introduction

Ensuring a reliable water supply is not only crucial for human survival but also fundamental for agricultural growth and energy production [1]. However, rapid population growth, increasing urbanization, and expanding economic activities [2] have placed unprecedented pressure on existing water resources, highlighting the urgency of implementing sustainable water management strategies and exploring alternative water sources to enhance resilience and ensure long-term water security. Climate variability further compounds these challenges, necessitating adaptive strategies to safeguard water availability.

Many researchers have focused their research on improving efficiency and exploring alternative sources of water; references [3,4] investigated different methods of improving water usage efficiency in agricultural, industrial, and domestic settings, whilst references [5,6] explored different alternative sources of water, such as by harvesting rainwater and fog, and through recycling of wastewater. Additionally, sustainable stormwater management solutions, including retention tanks and rain gardens, have been shown to enhance local water reuse and mitigate stormwater overflows, contributing to sustainable urban water management [7]. Beyond these, non-conventional water resources—including desalination, brackish and saline water treatment, and groundwater recharge—are increasingly recognized as viable alternatives to enhance water security, particularly under conditions of water scarcity [8,9]. Among these approaches, rainwater harvesting (RWH) stands out as a practical and environmentally friendly solution to supplement water supplies and promote sustainable water management practices, especially in tropical countries, which are blessed with abundant of rainfall.

In actual fact, RWH is a centuries-old method of water collection. RWH systems collect, store, and, in some cases, treat rainwater from rooftops or pavements, or other catchment areas for various applications [5]. They range from simple setups intended solely for water collection to more advanced setups that include water treatment to ensure water quality. Regardless of their complexity, all RWH systems consist of three main components: a catchment area to gather rainwater, a collection device to store the water, and a conveyance system to transport the water from the catchment area to a collection device and as well as to its point of use. By capturing and storing rainwater, RWH systems have been reported to achieve water savings of up to 60% [10]. Additionally, they also provide significant environmental benefits by reducing stormwater runoff, thereby mitigating floods and alleviating soil erosion and hence supporting the overall sustainability of the ecosystem [11]. The versatility of RWH allows for successful integration into a variety of contexts, including domestic [12], commercial [13], and agricultural [14] applications, across both urban [6,15] and rural settings [4,16]. For instance, harvested rainwater has been widely used for toilet flushing, contributing to urban water resilience and reducing dependence on municipal water supplies [17]. In commercial settings, RWH has been integrated into building water systems [13], while in agriculture, it has been utilized to supply aquaponic systems, with factors such as tank size and water tariffs influencing feasibility [14]. These applications highlight the potential of RWH systems as a viable strategy for sustainable water management, offering practical solutions to address water scarcity and conservation challenges.

The environmental and practical benefits of RWH systems make them particularly well-suited for regions with high water consumption and abundant rainfall, such as Brunei Darussalam. With a reported average water consumption rate of approximately 380 L per capita per day, the highest in the region, and a population growth expected to increase at an average annual rate of 1.1% [18], the country faces growing challenges in meeting water demand in the coming years [15]. To address these concerns, it is necessary to explore alternative water sources and adopt sustainable water management practices, as outlined in Brunei’s strategic plan [19]. With an annual rainfall of around 3000 mm, Brunei has significant potential to utilize RWH systems as an alternative water source. As a predominantly Muslim country, Brunei’s frequent water use for religious practices further underscores the relevance of integrating RWH systems. Ablution (wudhu), a mandatory religious practice that involves washing specific parts of the body before performing specified religious acts [20], is performed multiple times a day, resulting in substantial water consumption. Excessive amounts of water used during ablution (a common phenomenon among the general Muslims) not only place additional pressure on water resources but also contradict Islamic teachings, which emphasize avoiding wastage in all aspects [21]. Therefore, integrating RWH systems for ablution not only promotes the environmental and economic benefits of the system, but also aligns with Islamic values of promoting water conservation.

Previous studies have demonstrated the techno-economic feasibility of RWH systems, in general [12] and for ablution purposes [22], particularly within the context of Brunei. On the other hand, this study explores the social acceptance of the RWH system by assessing the public’s acceptance of RWH systems through survey questionnaires. An acceptance model based on the Technology Acceptance Model (TAM) framework was constructed along with proposed hypotheses. Data from the questionnaires were analyzed using descriptive statistics and regression analysis to test the proposed hypotheses. In addition to evaluating general public acceptance of RWH systems and the use of rainwater for non-potable and ablution purposes, this study also aims to provide insights to facilitate the wider adoption of RWH systems. The objectives of this study are directly aligned with the United Nations’ Sustainable Development Goals (SDGs), particularly SDG 6 (Clean Water and Sanitation), SDG 12 (Responsible Consumption and Production), and SDG 13 (Climate Action). By promoting sustainable water management practices such as RWH, this research supports efforts to ensure universal access to clean water (SDG 6), encourage efficient use of natural resources (SDG 12), and mitigate the impacts of climate change through adaptive practices (SDG 13). Integrating RWH systems, particularly in religious and cultural contexts, provides a practical and meaningful contribution to these global goals.

2. Methodology

This research employs a quantitative survey-based approach to assess public acceptance of Rainwater Harvesting (RWH) systems for non-potable uses and ablution purposes in Brunei Darussalam. The Technology Acceptance Model (TAM) framework, extended with external factors such as Subjective Knowledge (SK), Perceived Cost (PC), Technical Requirements (TR), and Perceived Risk (PR), was utilized to understand the relationships influencing public acceptance. In addition to the TAM-based constructs, the study included questions exploring practical applications of RWH systems, public perceptions of government initiatives, and cultural considerations for ablution.

A structured questionnaire was developed to measure the TAM constructs and capture broader insights into practical and cultural considerations. The questionnaire was pilot-tested and refined to ensure clarity and reliability before being distributed to a diverse sample through an online survey. Data collected were then analyzed using descriptive statistics and regression analysis to evaluate the hypotheses derived from the extended TAM framework. Findings from the TAM analysis and the extended questions aim to provide actionable insights for promoting RWH adoption and addressing public concerns within the local context.

2.1. Study Design

This study followed a systematic process to ensure the reliability and validity of the survey-based methodology. The process included the development and refinement of a structured questionnaire, ethics approval, pilot testing, survey distribution, and data collection. Figure 1 provides an overview of the research methodology.

2.1.1. Questionnaire Development

The questionnaire was designed to operationalize the constructs of the extended Technology Acceptance Model (TAM) framework, which was applied to assess public acceptance of Rainwater Harvesting (RWH) systems and recycled rainwater applications. This included measuring core TAM constructs such as Perceived Ease of Use (PEU), Perceived Usefulness (PU), Attitude Towards Use (ATU), and Intentions to Use (ITU), along with external factors including Subjective Knowledge (SK), Technical Requirements (TR), Perceived Cost (PC), and Perceived Risk (PR).

In addition to these theoretical constructs, the questionnaire included sections aimed at capturing broader insights into practical applications of RWH systems, public perceptions of government initiatives, and cultural considerations for ablution. These additional topics complemented the TAM framework, broadening the scope of the study.

The structured questionnaire underwent iterative refinement through pilot testing to ensure clarity, alignment with study objectives, and reliability. A 5-point Likert scale, ranging from “Strongly Disagree” to “Strongly Agree”, was employed for most items, while categorical questions included descriptive options to accommodate participant reasoning where applicable.

2.1.2. Ethics Approval

Prior to data collection, the questionnaire and study design were submitted to the Faculty Research Ethics Committee for review and approval. Ethical considerations were meticulously addressed to ensure the study adhered to research guidelines and protected participant rights throughout. Specific measures included:

• Confidentiality and Anonymity: All responses were anonymized, and data were stored securely to prevent unauthorized access.
• Informed Consent: Participants were provided with a detailed explanation of the study objectives, the voluntary nature of their participation, and their right to withdraw at any stage without consequences.
• Sensitivity to Cultural and Religious Topics: Special attention was given to questions related to ablution and religion. These questions were carefully crafted to avoid offense and respect cultural and religious sensitivities. Participants were assured that their responses would remain confidential and used solely for research purposes.

Ethics approval was obtained on 27th August 2024, ensuring that all aspects of the study complied with ethical research practices. The inclusion of culturally and religiously sensitive questions was handled with appropriate guidance, and all data collection adhered to the approved protocols.

2.1.3. Pilot Study

A pilot study was conducted with eight (8) participants from diverse demographic backgrounds to evaluate the clarity, reliability, and effectiveness of the questionnaire. Feedback was gathered on:

• The clarity of instructions and questions.
• The time required to complete the questionnaire.
• Any ambiguous or redundant items.

The results of the pilot study informed the refinement of the questionnaire to enhance its usability and alignment with the research objectives.

2.1.4. Refinement of Questionnaire

Based on the feedback from the pilot study, several adjustments were made to the questionnaire:

• Rephrasing ambiguous questions to improve clarity.
• Reducing redundancy by merging overlapping items.
• Adjusting the layout to ensure better flow and participant engagement.

The refined questionnaire was finalized for distribution and reviewed by the researchers for further validation.

2.1.5. Survey Distribution and Data Collection

The finalized questionnaire was designed and hosted on the Qualtrics survey platform, providing a user-friendly interface for respondents and ensuring data security during collection. The survey link was distributed via email and WhatsApp to reach a diverse sample from Brunei Darussalam. The survey period spanned from 7 September 2024 to 30 November 2024, a duration of nearly 3 months.

To ensure statistical representativeness, the target sample size was calculated based on Brunei’s total population of 450,500. Using a confidence level of 95% and a margin of error of ±5%, the required sample size was determined to be 384 respondents. This sample size ensures sufficient statistical power for analyzing the constructs outlined in the study framework. A non-probability convenience sampling approach was adopted, leveraging digital platforms to maximize participation while ensuring broad demographic coverage. While probability sampling would have been ideal, practical constraints—including time, resource limitations, and ethical considerations related to participant recruitment—necessitated the use of convenience sampling, with online distribution via WhatsApp and email employed to maximize accessibility. The inclusion criteria required that respondents:

• Be at least 15 years old.
• Reside in Brunei Darussalam.

During the survey period, responses were monitored for participation rates to ensure representativeness across demographic groups. Efforts were made to encourage participation from underrepresented groups by distributing reminders and extending the survey period where necessary. Upon survey closure, all responses were downloaded from Qualtrics and underwent a rigorous cleaning process to exclude incomplete or invalid entries. The cleaned dataset was finalized for analysis, ensuring it captured both TAM-related constructs and additional exploratory insights for a comprehensive assessment of public perceptions, attitudes, and intentions regarding RWH systems and recycled rainwater.

2.1.6. Data Analysis and Hypotheses Testing

The data collected from the survey were analyzed to evaluate the relationships between the constructs outlined in the study’s conceptual framework and to explore broader insights into public acceptance of Rainwater Harvesting (RWH) systems. Descriptive statistics were used to summarize demographic characteristics, such as age, gender, and education level, as well as general response patterns regarding attitudes toward Rainwater Harvesting (RWH) systems. These analyses provided an overview of the dataset and served as a foundation for more detailed inferential analysis.

Inferential analysis was conducted using multiple linear regression models to test the hypotheses derived from the extended TAM frameworks (for both general RWH systems and recycled rainwater applications). The regression analysis examined the relationships between dependent and independent variables, assessing the significance and strength of these associations. Separate regression models were developed for:

• The general RWH systems framework, identifying predictors of public acceptance based on TAM constructs and external factors.
• The recycled rainwater framework, focusing on the context-specific factors influencing acceptance.

For broader insights (practical applications, government initiatives, and cultural considerations), categorical and descriptive analyses were conducted to identify trends and preferences without hypothesis testing.

All analyses were performed using MS Excel and MATLAB R2023B, which facilitated the computation of descriptive summaries and regression models. Key metrics analyzed included R² values, to determine the proportion of variance explained by the models; p-values, to assess statistical significance; regression coefficients, to measure the strength and direction of relationships; and t-values, to evaluate the relative contribution of each independent variable. A significance threshold of p < 0.05 was applied throughout.

This analytical approach provided robust insights into the factors influencing public acceptance of RWH systems and recycled rainwater applications. In addition, it captured preferences for practical applications, perceptions of government initiatives, and cultural considerations for ablution. These findings form the basis for the detailed results and discussions presented in subsequent sections.

2.2. Research Framework and Hypotheses

2.2.1. Research Framework

The research framework is based on the Technology Acceptance Model (TAM) framework, which was developed to assess public acceptance of technology [23]. TAM predicts the acceptance of a new technology and assesses the factors influencing public attitude toward it. The framework is rooted in the belief–attitude–intention–behavior causal relationship [24] and comprises of four main constructs:

• Perceived Ease of Use (PEU): The extent to which a person believes using a technology requires minimal effort.
• Perceived Usefulness (PU): The degree to which a person believes a technology enhances their performance.
• Attitude Towards Use (ATU): Refers to the overall evaluation, whether positive or negative, of using the technology.
• Intentions to Use (ITU): Represents the likelihood of adopting the technology.

Several external factors can influence PU and PEU. To assess the public’s acceptance of Rainwater Harvesting (RWH) systems, this study incorporates the following external factors into the TAM framework:

• Subjective Knowledge (SK): The extent to which an individual believes they understand RWH systems based on personal experience.
• Technical Requirements (TR): The perceived complexity of installation, maintenance, and operational needs of the system.
• Perceived Cost (PC): The financial burden associated with adopting and maintaining RWH systems.
• Perceived Risk (PR): Concerns about potential risks, such as water quality and system reliability.

Two variations of the extended TAM framework were utilized in this study to assess public acceptance of RWH systems and recycled rainwater applications. These two frameworks capture different aspects of public perception, as they address distinct applications of rainwater use.

• The first framework, visualized in Figure 2a, focuses on the public acceptance of RWH systems for general non-potable uses, such as irrigation and household cleaning. This model emphasizes external factors like SK, TR, and PC, which influence people’s willingness to adopt RWH systems. It particularly highlights infrastructure-related barriers, including cost concerns, lack of awareness, and perceived technical complexity.
• The second framework, visualized in Figure 2b, focuses on recycled rainwater applications, where safety and quality concerns are critical. Unlike the first framework, where technical and financial factors dominate, this model emphasizes Perceived Risk (PR) as a critical factor, reflecting the psychological and trust-based barriers to adopting recycled water for purposes such as ablution. Since recycled rainwater has undergone storage but no formal treatment, concerns about water quality, safety, and hygiene influence public perceptions and trust.

These frameworks differ in their scope, focus, and the key external factors they emphasize. While both models contribute to understanding public acceptance of rainwater use, they serve distinct purposes—one focusing on technical and financial feasibility, while the other explores psychological and trust-based barriers to adoption. A detailed comparison is provided in

Table 1. Comparison of the extended TAM frameworks for (a) general Rainwater Harvesting systems and (b) recycled rainwater applications.

Aspect	Framework (a): RWH Systems	Framework (b): Recycled Rainwater
Scope	General use of rainwater (e.g., irrigation, cleaning)	Specific to recycled rainwater (e.g., for ablution)
Key External Factors	Subjective Knowledge (SK), Perceived Cost (PC), Technical Requirement (TR)	Perceived Risk (PR)
Primary Barriers	Financial cost, technical complexity	Health and safety concerns
Focus	Infrastructure feasibility and general acceptance	Trust, quality assurance, and psychological acceptance

, highlighting how the two frameworks complement one another to provide a comprehensive understanding of public acceptance of both general and specialized rainwater applications.

2.2.2. Research Hypotheses

This study applies an extended Technology Acceptance Model (TAM) to assess the factors influencing public acceptance of Rainwater Harvesting (RWH) systems and recycled rainwater applications. The model incorporates both core TAM constructs and external factors to provide a comprehensive understanding of the key drivers and barriers affecting adoption.

The core TAM constructs—Perceived Ease of Use (PEU), Perceived Usefulness (PU), Attitude Towards Use (ATU), and Intentions to Use (ITU)—form the foundation of the framework. In addition, external factors, including Subjective Knowledge (SK), Perceived Cost (PC), Technical Requirements (TR), and Perceived Risk (PR), are incorporated to examine additional influences on acceptance. Figure 2a,b illustrate the hypothesized relationships for both general RWH systems and recycled rainwater applications, with hypotheses structured accordingly.

Core TAM Constructs Hypotheses

The core constructs of the TAM framework serve as the foundation for understanding public acceptance of RWH systems and recycled rainwater applications. These constructs—Perceived Ease of Use (PEU), Perceived Usefulness (PU), Attitude Towards Use (ATU), and Intentions to Use (ITU)—describe how individuals develop attitudes toward adopting a system and form intentions to use it.

• Perceived Ease of Use (PEU) reflects the degree to which a system is perceived as easy to use. A system that is easy to use is expected to enhance perceptions of its usefulness, as users find it more convenient and practical [25].
• Perceived Usefulness (PU) refers to the extent to which RWH systems and recycled rainwater applications are perceived as beneficial in meeting water needs and improving efficiency [26].
• Attitude Towards Use (ATU) captures the overall evaluation of the system, where both PEU and PU influence how positively or negatively individuals view adoption [23].
• Intentions to Use (ITU) measure an individual’s likelihood of adopting RWH systems and recycled rainwater applications, which is strongly influenced by their attitude towards use [23].

These relationships form the core pathways of the TAM framework, where PEU and PU directly shape ATU, and ATU ultimately influences ITU. The following hypotheses are proposed to examine these relationships:

• H1: PEU → PU: Perceived Ease of Use positively influences Perceived Usefulness.
• H2: PU → ATU: Perceived Usefulness positively influences Attitude Towards Use.
• H3: PEU → ATU: Perceived Ease of Use positively influences Attitude Towards Use.
• H4: ATU → ITU: Attitude Towards Use positively influences Intentions to Use.

These core pathways, as visualized in both Figure 2a,b, provide a foundation for analyzing public acceptance of RWH systems and recycled rainwater applications.

External Factors Hypotheses

In addition to the core TAM constructs, four external factors—Subjective Knowledge (SK), Perceived Cost (PC), Technical Requirements (TR), and Perceived Risk (PR)—are introduced to capture other influences on adoption.

• Subjective Knowledge

Subjective Knowledge (SK), depicted in Figure 2a, represents an individual’s perceived understanding of RWH systems based on personal experience or prior knowledge [27]. Higher SK is expected to enhance the perceived benefits of the system, leading to improved attitudes and stronger intentions to adopt RWH systems [28]. Therefore, the following hypotheses are proposed:

• H5: SK → PU: Subjective Knowledge positively influences Perceived Usefulness.
• H6: SK → ATU: Subjective Knowledge positively influences Attitude Towards Use.
• H7: SK → ITU: Subjective Knowledge positively influences Intentions to Use.

• Perceived Cost (PC)

Perceived Cost (PC) is illustrated in Figure 2a,b, and reflects concerns about the financial burden associated with adopting and maintaining RWH systems, and utilizing recycled rainwater, respectively. Higher PC is expected to reduce the perceived ease of use and usefulness of the system, negatively affecting attitudes and intentions [29], as cost concerns may deter individuals from considering these systems as practical alternatives. The following hypotheses are proposed:

• H8: PC → PEU: Perceived Cost negatively influences Perceived Ease of Use.
• H9: PC → PU: Perceived Cost negatively influences Perceived Usefulness.
• H10: PC → ATU: Perceived Cost negatively influences Attitude Towards Use.
• H11: PC → ITU: Perceived Cost negatively influences Intentions to Use.

• Technical Requirements (TR)

Technical Requirements (TR), also shown in Figure 2a, capture perceptions of the complexity of installing, maintaining, and operating RWH systems. Higher PC is expected to reduce perceived ease of use, usefulness, and overall acceptance, as individuals may perceive the system as too difficult to implement or maintain [30]. Thus, the following hypotheses are proposed:

• H12: TR → PEU: Technical Requirements negatively influence Perceived Ease of Use.
• H13: TR → PU: Technical Requirements negatively influence Perceived Usefulness.
• H14: TR → ATU: Technical Requirements negatively influence Attitude Towards Use.
• H15: TR → ITU: Technical Requirements negatively influence Intentions to Use.

• Perceived Risk (PR)

Perceived Risk (PR), as depicted in Figure 2b, captures concerns about the safety, reliability, and quality of rainwater, particularly in recycled applications [5]. Higher PR is expected to decrease the perceived benefits and overall acceptance of the system, as individuals may hesitate to adopt a system they perceived as unsafe or unreliable. The following hypotheses are proposed:

• H16: PR → PU: Perceived Risk negatively influences Perceived Usefulness.
• H17: PR → ATU: Perceived Risk negatively influences Attitude Towards Use.
• H18: PR → ITU: Perceived Risk negatively influences Intentions to Use.

By testing these hypotheses, which are represented in Figure 2a for RWH systems and Figure 2b for recycled rainwater applications, this study aims to identify the factors that most significantly influence public attitudes and intentions. This approach provides a comprehensive framework for understanding barriers and enablers to adopting sustainable water management practices.

2.3. Questionnaire Design

The finalized questionnaire was structured to align with the objectives of the study and the constructs of the extended Technology Acceptance Model (TAM) frameworks, as described in the previous section, while also addressing broader insights into public perceptions and practical applications of Rainwater Harvesting (RWH) systems. It consisted of five sections:

• Section A: Demographics and Background Information
  Collected respondent characteristics such as age, gender, education level, and household size, providing contextual data for analysis.
• Section B: Acceptance of General RWH Systems
  Focused on constructs from the extended TAM framework for general non-potable uses of RWH systems, including Perceived Ease of Use (PEU), Perceived Usefulness (PU), Attitude Towards Use (ATU), Intentions to Use (ITU), and external factors such as Subjective Knowledge (SK), Technical Requirements (TR), and Perceived Cost (PC). Example: “I believe that RWH systems can have positive impacts on the environment”.
• Section C: Perceptions of Recycled Rainwater Applications
  In addition to the extended TAM framework (PEU, PU, ATU, and ITU), this section also explored the role of Perceived Cost (PC) and Perceived Risk (PR) as external factors in influencing public perceptions of recycled rainwater applications. The constructs emphasize safety, trust, and feasibility associated with recycled rainwater applications. Example: “I believe that the recycling of rainwater is useful for water conservation”.
• Section D: Practical and Policy Considerations for RWH Systems
  Explored broader topics such as acceptable non-potable uses of harvested rainwater and public perceptions of government initiatives to promote RWH adoption.
• Section E: Cultural and Religious Considerations for Ablution
  Focused on perceptions of using recycled rainwater for ablution, including religious permissibility, water usage habits, and willingness to adopt specific practices such as using water pots. Example: “Do you think it is permissible in Islam to use harvested rainwater for ablution?”.

The questionnaire items were developed based on an extensive review of the literature to ensure alignment with the study objectives and the TAM constructs described in Section 2.2. Additional questions in Sections D and E were designed to broaden the scope of the study, addressing practical applications, policy initiatives, and cultural considerations. The iterative refinement process, involving expert feedback and pilot testing, ensured clarity, relevance, and reliability. Cronbach’s Alpha was used to assess internal consistency, with all constructs achieving acceptable values above 0.7.

Most questions employed a 5-point Likert scale, ranging from 1 (Strongly Disagree) to 5 (Strongly Agree), to capture nuanced attitudes and perceptions. Responses were collapsed into three categories—Disagree (1–2), Neutral (3), and Agree (4–5)—for simplicity in trend reporting. For categorical questions, such as those in Sections D and E, descriptive options allowed respondents to provide detailed preferences or reasoning.

The structured questionnaire served as the primary tool for data collection, systematically capturing responses aligned with the extended TAM frameworks and broader study objectives. By combining theoretical constructs with practical and cultural insights, the questionnaire provided a robust basis for evaluating public attitudes, perceptions, and behavioral intentions toward RWH systems and recycled rainwater.

3. Results

An online Qualtrics questionnaire, as provided in Supplementary Material S1, was distributed via email and WhatsApp between 7th September 2024 and 30th November 2024 to a diverse group of participants across Brunei Darussalam. The target population included individuals aged 15 years and above, representing approximately 76% of Brunei’s total population of 450,500. With a 95% confidence interval (CI) and a margin of error (MoE) of ±5%, the calculated target sample size was 384 respondents. During the survey period, responses were collected from 403 participants, exceeding the target and ensuring enhanced reliability and representativeness of the findings.

3.1. Demographic and Background Characteristics

The survey captured responses from 403 participants, reflecting a diverse demographic composition. Gender distribution (Figure 3a) indicates a higher proportion of female respondents, comprising 63.5% of the sample, while males accounted for 36.5%. While this distribution ensures representation from both genders, the study did not specifically analyze gender-based differences in perceptions of RWH systems; an interesting direct for future research is whether attitudes, perceived barriers, or willingness to adopt RWH systems vary by gender. Participants represented a wide range of age groups, with the majority (63.9%) falling within the 15–25 years category, followed by smaller proportions in the 26–35 years (11.5%) and 46–55 years (10.8%) groups (Figure 3b). Other age categories, including 36–45 years, 56–65 years, and those aged 66 and above, collectively accounted for the remaining 13.8%. The strong representation of younger respondents offers valuable insights into the views of a generation more likely to engage with sustainability initiatives [31]. However, the age distribution does not fully align with the general Bruneian population, where the median age is 32.2 years. This discrepancy is likely due to the survey’s online distribution via WhatsApp and email, which naturally favored younger and digitally active individuals. Consequently, older individuals and those with limited digital access were underrepresented, despite Brunei’s high internet penetration rate (~99%). This limitation underscores the need for future research to employ more inclusive survey methods, such as in-person or stratified sampling approaches, to ensure broader demographic representation.

Ethnic composition (Figure 3c) was predominantly Malay, making up 82.4% of respondents, with smaller proportions of Chinese (11.2%), Indian (0.3%), and other ethnicities (6.1%). This distribution aligns closely with Brunei’s national demographics, ensuring cultural relevance in analyzing public acceptance of RWH systems. In terms of religious affiliation, the majority of respondents identified as Muslim (87.2%), reflecting the dominant religious group in Brunei. Other affiliations included Buddhism (6.8%), Christianity (3.0%), and other religions (3.0%) (Figure 3d). It is important to note that only Muslim respondents were eligible to answer questions in Section E, which focused on cultural and religious considerations related to ablution.

The sample exhibited a well-educated population, with over half of respondents (56.1%) holding an undergraduate degree and an additional 13.2% reporting postgraduate qualifications (Figure 3e). Other respondents indicated completion of O-Level (6.1%), A-Level (12.8%), or diploma-level education (11.8%). This higher-than-average educational attainment suggests respondents were more likely to be familiar with environmental and technological concepts, which may have influenced their perceptions of RWH systems. This trend is reflective of the digital outreach strategy used in survey distribution, as individuals with higher education levels are generally more engaged with sustainability discussions and emerging technologies.

While this demographic profile provides meaningful insights from early adopters and individuals more likely to drive future adoption, it does not fully capture the perspectives of the broader Bruneian population. However, according to Bass Diffusion Theory, early adopters play a crucial role in driving future adoption [32] by influencing later adopters through demonstration and advocacy. Their perceptions and willingness to adopt RWH systems provide meaningful indications of potential long-term acceptance trends. Nonetheless, to ensure a more comprehensive assessment of public attitudes, future studies should incorporate more diverse sampling methods, including in-person surveys and stratified sampling approaches, to capture perspectives across various age groups, education levels, and occupational sectors. Naturally, such approaches would require additional resources, including time, funding, and logistical support, to effectively reach underrepresented groups. Balancing feasibility with inclusivity remains a key consideration in expanding future research on public acceptance of RWH systems.

3.2. Acceptance of General RWH System

Rainwater Harvesting Systems (RWHs) have been historically used as a sustainable method to collect and store rainwater from various surfaces, such as rooftops and pavements. RWH systems can be utilized for both potable purposes, such as drinking and cooking, and non-potable purposes, which include applications like irrigation, cleaning, and toilet flushing. In this study, non-potable purposes are defined to encompass uses that do not involve direct consumption but significantly contribute to water conservation and sustainability efforts.

In this study, respondents were asked about their ownership of RWH systems. The results revealed that a small proportion of participants, approximately 12.84%, reported owning a functional RWH system in their households, as depicted in Figure 4. This low ownership rate underscores potential barriers to adoption of RWH systems in the country despite their recognized sustainability benefits [12,22].

To evaluate public acceptance of RWH systems, the extended Technology Acceptance Model (TAM) framework (Figure 2a) was applied. This framework explores key constructs influencing acceptance, including Perceived Ease of Use (PEU), Perceived Usefulness (PU), Attitude Towards Use (ATU), and Intentions to Use (ITU), alongside external factors such as Subjective Knowledge (SK), Technical Requirements (TR), and Perceived Cost (PC). These constructs were operationalized through survey items in Section B of the questionnaire (Supplementary Material S1).

Figure 5 presents a detailed summary of public perceptions of RWH systems, categorized as positive, neutral, or negative. To ensure consistency across the constructs in the analysis and visualizations, responses to negatively framed items in the survey—PC1, PC2, and TR1—were flipped to align with a positive interpretation. This adjustment allows the visualization of Perceived Cost (PC) and Technical Requirements (TR) as favorable (e.g., “low cost” or “space-saving”) rather than unfavorable (e.g., “high cost” or “space-consuming”). This consistent presentation across constructs facilitates a more intuitive interpretation of the results, aligning PC and TR with positively framed constructs such as Perceived Ease of Use (PEU) and Perceived Usefulness (PU).

The findings indicate mixed levels of familiarity with RWH systems. While public familiarity with the concept of RWH systems (SK1) was somewhat divided, positive responses accounted for 37.50%, slightly exceeding other categories. In contrast, perceptions of Perceived Usefulness (PU) were notably high. Respondents expressed strong confidence in the reliability of RWH systems as a sustainable water source (PU1, 77.70%) and in their environmental benefits (PU2, 82.77%), highlighting a broadly favorable view of the potential impact of these systems.

Perceived Cost (PC) was identified as a potential barrier to adoption. Nearly half of the respondents (49.32% for both PC1 and PC2) perceived installation and maintenance costs as expensive. Only a small proportion (around 13%) viewed costs as favorable, while the remaining responses were neutral. These results suggest that cost concerns remain significant and could deter widespread adoption of RWH systems. Technical Requirements (TR) also posed challenges, particularly the perception of space requirements for RWH systems (TR1). With only 17.91% of respondents agreeing that RWH systems do not require significant space, the majority expressed neutral or negative views. This indicates that space considerations may represent an additional technical barrier to adoption, particularly in densely populated or space-constrained areas.

Despite these challenges, respondents demonstrated a generally positive Attitude Towards Use (ATU) of RWH systems. Most agreed that adopting RWH systems is feasible (ATU1) and expressed support for their use (ATU2) and further development (ATU3). Importantly, 67.23% of respondents indicated a willingness to adopt RWH systems at home when they become available (ITU1). These results highlight the public’s openness to RWH systems, provided that key concerns—particularly cost and technical barriers—are addressed.

Overall, the findings emphasize the importance of addressing perceived cost and technical requirements while leveraging the positive environmental perceptions and general attitudes toward RWH systems to drive broader adoption. To further elucidate these relationships, regression analysis was employed to evaluate the constructs of the extended Technology Acceptance Model (TAM) framework, along with the external factors. Hypotheses were considered supported if the p-value obtained was less than the significance threshold of 0.05 and the F-statistic exceeded a value of 1. The results, summarized in

Table 2. Summary of hypotheses testing with regression results for extended TAM framework for assessing public acceptance of general Rainwater Harvesting (RWH) systems.

Hypotheses	R2 Value	Coefficient	t-Value	p-Value	F-Stat	Test Result
H1: PEU → PU	0.097	0.354	5.61	<0.05	31.6	Supported
H2: PU → ATU	0.246	0.408	9.80	<0.05	96.0	Supported
H3: PEU → ATU	0.181	0.398	8.07	<0.05	65.1	Supported
H4: ATU → ITU	0.396	0.856	13.9	<0.05	193	Supported
H5: SK → PU	0.087	0.195	5.30	<0.05	28.1	Supported
H6: SK → ATU	0.061	0.134	4.36	<0.05	19.0	Supported
H7: SK → ITU	0.086	0.217	5.26	<0.05	27.6	Supported
H8: PC → PEU	0.171	−0.358	−7.80	<0.05	60.8	Supported
H9: PC → PU	0.001	−0.036	−0.622	>0.05	0.387	Rejected
H10: PC → ATU	0.013	−0.093	−2.00	<0.05	3.99	Supported
H11: PC → ITU	0.029	−0.186	−2.96	<0.05	8.74	Supported
H12: TR → PEU	0.065	−0.202	−4.53	<0.05	20.5	Supported
H13: TR → PU	0.003	−0.047	−0.891	>0.05	0.794	Rejected
H14: TR → ATU	0.019	−0.103	−2.40	<0.05	5.77	Supported
H15: TR → ITU	0.061	−0.248	−4.37	<0.05	19.1	Supported

, highlight significant findings that validate the extended TAM framework for acceptance of general RWH systems.

These findings provide comprehensive insights into the relationships outlined in the extended TAM framework in Figure 2a. Relationships among the Core TAM constructs were strongly supported, underscoring their validity. Perceived Ease of Use (PEU) significantly influenced Perceived Usefulness (PU) (H1: PEU → PU, β = 0.354, t = 5.61, p < 0.05, R² = 0.097). Although the R² value indicates that only 9.7% of the variance in PU is explained, the moderate β coefficient highlights the importance of usability in shaping perceptions of usefulness. Both PEU and PU emerged as significant predictors of Attitude Towards Use (ATU) (H2: PU → ATU, β = 0.408, t = 9.80, p < 0.05, R² = 0.246; H3: PEU → ATU, β = 0.398, t = 8.07, p < 0.05, R² = 0.181). The relationship between ATU and Intentions to Use (ITU) (H4: ATU → ITU, β = 0.856, t = 13.9, p < 0.05, R² = 0.396) demonstrated the strongest predictive power, with nearly 40% of the variance in ITU explained by ATU. These results reinforce the central role of attitudes in shaping behavioral intentions, as suggested by the TAM framework.

The external factors offered a nuanced perspective on public acceptance. Subjective Knowledge (SK) positively influenced PU, ATU, and ITU (H5: SK → PU, β = 0.195, t = 5.30, p < 0.05, R² = 0.087; H6: SK → ATU, β = 0.134, t = 4.36, p < 0.05, R² = 0.061; H7: SK → ITU, β = 0.217, t = 5.26, p < 0.05, R² = 0.086). These relationships, though associated with low R² values, suggest that familiarity with RWH systems contributes to positive perceptions, even if its influence is less substantial compared to core constructs such as PU or ATU.

Affordability emerged as a critical barrier to adoption. Perceived Cost (PC) negatively influenced PEU, ATU, and ITU (H8: PC → PEU, β = −0.358, t = −7.80, p < 0.05, R² = 0.171; H10: PC → ATU, β = −0.093, t = −2.00, p < 0.05, R² = 0.013; H11: PC → ITU, β = −0.186, t = −2.96, p < 0.05, R² = 0.029). However, no significant direct effect of PC on PU was observed (H9: PC → PU, β = −0.036, t = −0.622, p > 0.05, R² = 0.001). These findings underscore the importance of addressing cost concerns to improve the public’s willingness to adopt RWH systems.

Practical constraints posed another challenge to acceptance. Technical Requirements (TR) negatively impacted PEU, ATU, and ITU (H12: TR → PEU, β = −0.202, t = −4.53, p < 0.05, R² = 0.065; H14: TR → ATU, β = −0.103, t = −2.40, p < 0.05, R² = 0.019; H15: TR → ITU, β = −0.248, t = −4.37, p < 0.05, R² = 0.061). The relatively modest R² values indicate that other infrastructural or contextual factors may also play a role in shaping these perceptions.

These findings highlight the multifaceted nature of public acceptance of general RWH systems. While many R² values were low (<0.10), several key relationships stood out with moderate or high explanatory power. PEU → PU and PU → ATU exhibited moderate R² values (0.10–0.30), whilst PEU → ATU and PC → PEU demonstrated higher R² values, indicating a more substantial proportion of variance explained by these relationships. The strongest relationship was observed for ATU → ITU, with a β coefficient of 0.856 and an R² value of 0.396. This underscores the central role of attitudes in driving behavioral intentions. These relationships collectively validate the TAM framework’s predictive power in understanding the acceptance of RWH systems. Furthermore, eleven hypotheses demonstrated moderate β coefficients (0.10–0.50).

From a practical perspective, these findings offer valuable insights for fostering the adoption of RWH systems. Strong relationships like PEU → ATU and PC → PEU emphasize the importance of usability and affordability in shaping public attitudes and perceptions. The strong predictive power of ATU → ITU highlights the need to cultivate positive attitudes through strategies that enhance perceived ease of use and usefulness. Addressing barriers such as perceived cost and technical requirements remains critical for encouraging broader adoption. Additionally, targeted educational efforts to increase familiarity with RWH systems and their benefits can significantly improve public perceptions and behavioral intentions. By integrating external factors into the TAM framework, this study provides a comprehensive understanding of the drivers and barriers to public acceptance, offering actionable insights for advancing sustainable water management practices.

3.3. Perceptions of Recycled Rainwater Applications

Figure 6 provides a summary of public perceptions regarding the use of recycled rainwater for non-potable purposes. The responses were categorized as positive (agree and strongly agree), neutral, or negative (disagree and strongly disagree), reflecting the public’s views on the practicality, benefits, safety concerns, and willingness to adopt recycled rainwater applications. Similar to the adjustments made for Figure 4, responses to negatively framed questions, such as those for Perceived Risk (PR1 and PR2), were flipped for consistency. This ensures that all constructs are presented in a positive direction, facilitating a unified and intuitive interpretation of the results.

Respondents expressed strong agreement on the benefits of rainwater recycling. Nearly all participants responded positively (83.78%) or neutrally (15.88%) to the statement that recycling rainwater increases the supply of water available for non-potable purposes (PU1). Similarly, 80.41% agreed that recycling rainwater can reduce reliance on municipal water supplies (PU2), with only a small percentage (2.36%) disagreeing. When asked about the usefulness of rainwater recycling for water conservation (PU3), an overwhelming 87.84% agreed, with almost no respondents (0.68%) disagreeing. Additionally, respondents recognized financial benefits, with 83.45% agreeing that recycling rainwater can reduce municipal water bills (PC1), and only 1.35% expressing disagreement. These findings highlight a strong public recognition of the practical and economic advantages of rainwater recycling.

In terms of the ease of using recycled rainwater for non-potable purposes (PEU1), 63.18% of respondents agreed that the process is easy, indicating a generally positive perception of its practicality. However, 3.38% disagreed, suggesting that while the majority find it manageable, some challenges or uncertainties may still exist for a minority of the population.

Concerns about the safety and quality of recycled rainwater were widely reported, with 64.73% of respondents expressing concerns about the safety of collected rainwater (PR1) and 68.84% expressing concerns about the quality of recycled rainwater (PR2). These indicate heightened awareness of potential risks, but whether these concerns translate into actual reluctance to adopt remains an open question. Addressing public trust through transparent quality assurances, institutional oversight, and public awareness campaigns could play a key role in shaping broader acceptance.

Despite these concerns, there was strong support for rainwater recycling among respondents. More than three-quarters (78.42%) agreed that they support the practice (ATU1), with only 1.03% disagreeing. Additionally, 64.73% indicated that they would recommend rainwater recycling to others (ATU2), demonstrating broad public endorsement. The willingness to adopt recycled rainwater for non-potable purposes was also high, with 73.54% of respondents expressing their intention to use recycled rainwater (ITU1).

Overall, the findings highlight strong public recognition of the benefits of rainwater recycling, particularly in terms of water conservation, financial savings, and reducing dependence on main water supplies. While concerns about safety and quality were acknowledged, the relationship between these concerns and actual acceptance levels is further examined through regression analysis. Nonetheless, the strong support and willingness to adopt suggests that there is significant potential for successful implementation of rainwater recycling initiatives. The relationships between the constructs of the extended Technology Acceptance Model (TAM) framework, along with the external factors, were evaluated using regression analysis; with hypotheses considered supported if the p-value obtained was less than the significance threshold of 0.05 and F-statistic has a value to be greater than 1.

The results of the hypotheses testing for the extended TAM framework evaluating public acceptance of recycled rainwater applications, as summarized in

Table 3. Summary of hypotheses testing with regression results for extended TAM framework for assessing public acceptance of recycled rainwater applications.

Hypotheses	R2 Value	Coefficient	t-Value	p-Value	F-Stat	Test Result
H1: PEU → PU	0.238	0.3366	9.58	<0.05	91.8	Supported
H2: PU → ATU	0.380	0.685	13.4	<0.05	180	Supported
H3: PEU → ATU	0.262	0.427	10.2	<0.05	104	Supported
H4: ATU → ITU	0.418	0.702	14.5	<0.05	212	Supported
H8: PC → PEU	0.145	0.413	7.07	<0.05	50.0	Supported
H9: PC → PU	0.470	0.558	16.2	<0.05	261	Supported
H10: PC → ATU	0.206	0.410	8.72	<0.05	76.1	Supported
H11: PC → ITU	0.164	0.398	7.60	<0.05	57.8	Supported
H16: PR → PU	0.000	0.017	0.384	>0.05	0.147	Rejected
H17: PR → ATU	0.002	0.037	0.773	>0.05	0.598	Rejected
H18: PR → ITU	0.010	−0.088	−1.70	>0.05	2.88	Rejected

, provide significant insights into the relationships between the constructs. Strong relationships were observed among the core constructs, emphasizing the robustness of the TAM framework in this context. Perceived Ease of Use (PEU) significantly influenced Perceived Usefulness (PU) (H1: PEU → PU, β = 0.337, t = 9.58, p < 0.05, R² = 0.238), with the R² value indicating that 23.8% of the variance in PU was explained by PEU. This highlights the importance of usability in shaping perceptions of usefulness. Both PU and PEU were also significant predictors of Attitude Towards Use (ATU) (H2: PU → ATU, β = 0.685, t = 13.4, p < 0.05, R² = 0.380; H3: PEU → ATU, β = 0.427, t = 10.2, p < 0.05, R² = 0.262). These moderate-to-high R² values reinforce the role of both usability and perceived benefits in shaping attitudes. The relationship between ATU and Intentions to Use (ITU) (H4: ATU → ITU, β = 0.702, t = 14.5, p < 0.05, R² = 0.418) demonstrated the strongest predictive power, explaining 41.8% of the variance in ITU, underscoring the central role of attitudes in influencing behavioral intentions toward adopting recycled rainwater applications.

The external factor of Perceived Cost (PC) also emerged as an important factor. PC significantly influenced PEU, PU, ATU, and ITU (H8: PC → PEU, β = 0.413, t = 7.07, p < 0.05, R² = 0.145; H9: PC → PU, β = 0.558, t = 16.2, p < 0.05, R² = 0.470; H10: PC → ATU, β = 0.410, t = 8.72, p < 0.05, R² = 0.206; H11: PC → ITU, β = 0.398, t = 7.60, p < 0.05, R² = 0.164). The highest R² value for H9 (47.0%) indicates a strong influence of cost on perceived usefulness, suggesting that affordability is a key determinant in shaping public perceptions of recycled rainwater systems. The moderate effects of PC on ATU and ITU further emphasize the importance of addressing cost-related concerns to foster broader acceptance.

On the other hand, Perceived Risk (PR) demonstrated no significant relationships with the TAM constructs, leading to the rejection of H16, H17, and H18 (H16: PR → PU, β = 0.017, t = 0.384, p > 0.05, R² = 0.000; H17: PR → ATU, β = 0.037, t = 0.773, p > 0.05, R² = 0.002; H18: PR → ITU, β = −0.088, t = −1.70, p > 0.05, R² = 0.010). These findings suggest that concerns about safety and trust in recycled rainwater systems, while important in descriptive analyses, did not exert measurable direct effects within this framework. However, this does not diminish the potential importance of perceived risk as an indirect or contextual factor influencing public acceptance.

Moderate R² values (0.10–0.30) for relationships such as PEU → PU (R² = 0.238) and PEU → ATU (R² = 0.262) highlight the model’s applicability in capturing public perceptions. The highest R² value, observed for PC → PU (R² = 0.470), indicates the significant role of affordability in shaping perceptions of usefulness, whilst the similarly strong R² value for ATU → ITU (R² = 0.418) underscores the centrality of attitudes in driving behavioral intentions within the extended TAM framework.

β coefficients further explain the strength of these relationships. The highest coefficient was observed for PC → PU (β = 0.558), further emphasizing the important influence of perceived cost on usefulness. Other key relationships, such as PU → ATU (β = 0.685) and ATU → ITU (β = 0.702), demonstrated strong predictive effects, underscoring the pivotal role of perceived usefulness and attitudes in fostering public acceptance. Moderate β values (0.10–0.50) for constructs such as PEU → PU, PEU → ATU, and PC → ATU suggest meaningful contributions to shaping acceptance. In contrast, the negligible coefficients and low R² values for constructs like Perceived Risk (PR) emphasize its minimal direct influence on public acceptance.

From a practical perspective, these findings provide actionable insights for fostering the adoption of recycled rainwater applications. Strong relationships such as PC → PU and PU → ATU emphasize the critical role of affordability and perceived usefulness in influencing public attitudes toward recycled rainwater applications, whilst the robust predictive power of ATU → ITU underscores the importance of cultivating positive attitudes through initiatives that enhance the perceived benefits and reliability of recycled rainwater applications. While concerns regarding perceived risk persist, ensuring public trust in water quality and safety remains essential for broader acceptance. Targeted outreach efforts, including educational campaigns that highlight the environmental and economic benefits of recycled rainwater systems, alongside assurances about water safety and compliance with cultural or religious values, can further enhance public willingness to adopt. By incorporating external factors such as cost and risk into the TAM framework, this study offers a nuanced understanding of the facilitators and obstacles to public acceptance, paving the way for more effective strategies to integrate recycled rainwater applications into sustainable water management solutions.

3.4. Broader Insights from Exploratory Questions

Respondents were asked to provide their perspectives on the acceptable uses of harvested rainwater, their views on government initiatives aimed at enhancing the adoption of rainwater harvesting (RWH) systems, and issues related to the use of rainwater for ablution purposes. Given that Brunei is a predominantly Muslim country where ablution constitutes a significant portion of daily water usage, understanding these aspects is crucial. These exploratory questions aim to uncover broader insights into practical, policy-related, and cultural considerations that influence the adoption and acceptance of RWH systems in the local context.

Figure 7 illustrates the distribution of responses as percentages of the total respondents, showing the acceptable non-potable uses for collected rainwater. Outdoor applications were the most commonly identified, with 93.0% of respondents indicating irrigation and 92.0% selecting cleaning outdoor areas as possible applications. These results highlight a strong inclination toward using harvested rainwater for practical, outdoor tasks that require substantial water quantities. Indoor applications, on the other hand, showed more variability in acceptance. Rainwater use for toilet flushing was identified by 64.3% of respondents. Cleaning indoor areas received less interest, with 36.4% of respondents indicating it as an acceptable use. Finally, kitchen use had the least support, with only 20.3% of respondents willing to consider this application, likely due to hygiene-related concerns.

The results suggest that while rainwater is widely regarded as suitable for certain non-potable applications, additional initiatives to address safety and quality concerns need to be made to broaden its acceptability for indoor uses.

Figure 8 illustrates the initiatives identified by respondents as necessary to enhance the adoption of Rainwater Harvesting (RWH) systems in the country. Among the five listed measures, the most frequently selected initiative was publicity and education on RWH systems, with 84.83% of respondents indicating it as essential. This finding aligns with earlier observations of divided responses regarding subjective knowledge of RWH systems, suggesting a need for widespread awareness campaigns to address knowledge gaps. The provision of installation and maintenance services also emerged as the second most supported initiative, with 77.59% of respondents highlighting its importance. Similarly, technical guidance was deemed critical by 72.76% of respondents, emphasizing the need for accessible expertise and resources to facilitate system adoption. Financial subsidies, often a key enabler for technology adoption, were selected by 61.03% of respondents. Wide implementation of pilot projects garnered support from 60.69% of respondents. While this was the least selected initiative, it still indicates that practical demonstrations of RWH systems could play a role in increasing public trust and acceptance.

These results highlight the critical importance of socio-studies in understanding the drivers of public acceptance for RWH systems. While our earlier studies [12] analyzed the effect of subsidies in improving economic feasibility, the findings from this study suggest that subsidies alone may not be sufficient. For example, initiatives like education, technical support, and maintenance services were found to have an even greater influence on fostering public acceptance and confidence in RWH systems. By prioritizing these areas, policymakers and stakeholders can design more effective strategies that go beyond financial incentives to address the social, informational, and technical dimensions of sustainable water management.

As has been shown in the demographic section, 87.2% of the respondents identified as Muslim. Their insights on water usage for ablution and the potential acceptance of using harvested rainwater for this purpose were explored. Daily water usage for ablution, summarized in Figure 9, highlights significant variability among respondents, both in the frequency of ablution (Figure 9a) and the amount of water used per session (Figure 9b). The majority of respondents (50.2%) reported performing ablution five times daily, consistent with the five main prayer requirements, with a considerable number (35.8%) exceeding this frequency and a smaller group performed ablution fewer than five times daily (14.0%). Water usage per session also varied significantly; among the respondents, 22.4% reported using less than 2 L per session, 26.4% used 2 to 5 L, 9.6% used 5 to 8 L, and a smaller group (2.4%) used more than 8 L per session. Additionally, 39.2% were unsure of their water usage. Given these variations, total daily water demand for ablution ranged from as little as 4 L to over 50 L per person. This wide range suggests that individual practices significantly influence overall water consumption, with some individuals using considerably more water than others. This variation underscores the potential for water conservation through awareness campaigns and more efficient water use practices in ablution.

Interestingly, nearly half (49.2%) of the respondents acknowledged that water is often wasted during ablution, as shown in Figure 10, when exploring attitudes toward water usage during this religious practice. This perspective highlights a significant awareness among respondents about inefficiencies in water use during ablution. However, 28.4% disagreed with the notion of water wastage, and 22.4% were unsure. This variability in perceptions may stem from differing habits or understanding of water efficiency. In fact, it is confirmed in Islamic tradition that 0.688 liters of water is sufficient for ablution [33]. Encouragingly, a large majority (83.2%) believed it is possible to reduce or avoid water wastage during ablution, with only a small proportion (4.4%) disagreeing with this possibility, and 12.4% remaining uncertain. These suggest that most respondents recognize the potential for improvements in water management during ablution and are open to practical solutions to achieve this.

In actual fact, theological implications of water wastage added a layer of complexity to the discussion on water conservation for this important religious practices. When asked whether wasting water during ablution could be considered Haram (forbidden in Islam), only 25.6% agreed, while a significant 47.2% were unsure, and 27.2% disagreed. This uncertainty highlights a need for religious education to better connect Islamic principles of conservation with daily practices. Clarifying the theological stance on water conservation could play a pivotal role in fostering more sustainable behaviors during ablution. In fact, religious motivation emerged as a powerful driver for water-saving practices, with 84.0% of respondents agreeing that it could influence Muslims to conserve water. This strong alignment between faith and environmental stewardship underscores the potential of leveraging religious teachings to encourage sustainable practices. Additionally, 87.15% of respondents expressed willingness to adopt water pots containing a fixed amount of water for ablution, reflecting receptiveness to traditional yet practical solutions. While rooted in Islamic history, such measures offer an opportunity to align spiritual values with modern sustainability goals, provided they meet the expectations of hygiene and convenience. These findings reinforce the potential for integrating cultural, religious, and practical considerations into strategies for water conservation during ablution, addressing both the substantial water demand and the principles of Islamic teachings.

Following the exploration of respondents’ attitudes toward water wastage and conservation during ablution, their views on the use of harvested rainwater for ablution were assessed. This line of inquiry sought to understand both theological acceptance and practical willingness, as well as community-level support for institutional initiatives involving rainwater.

Figure 11a summarizes responses to the question of whether using harvested rainwater for ablution is permissible in Islam. A significant majority of respondents (76.40%) agreed that this practice aligns with Islamic teachings, underscoring the compatibility of rainwater use with religious principles. This finding reflects the theological flexibility within Islam, particularly its emphasis on environmental stewardship and avoiding wastage. Only a minority expressed uncertainty or disagreement, suggesting that most respondents viewed the use of rainwater as a viable and acceptable alternative. The willingness to use harvested rainwater for ablution was also explored, with results summarized in Figure 11b. A positive response was observed among 73.49% of participants, indicating strong practical support for the adoption of such systems. However, 8.84% of respondents were unwilling, while 17.67% expressed uncertainty. Reasons for hesitancy, illustrated in Figure 11, were primarily tied to concerns about cleanliness (84.78%). A smaller proportion cited doubts about the religious permissibility of the practice (13.04%) or highlighted a lack of knowledge about using harvested rainwater for ablution (2.17%). In fact, the use of rainwater for ablution has been established in the Islamic tradition [34], with the Quran referring to rainwater as “purifying water” [35]. These findings emphasize the need for educational efforts, including from the perspective of the religion, to address misconceptions and promote confidence in the quality and safety of rainwater.

Building on the earlier findings regarding the importance of wide implementation initiatives for promoting rainwater harvesting systems, community-level efforts also emerged as a significant area of interest. When respondents were asked about their support for mosques and institutions offering harvested rainwater for ablution, more than half expressed agreement, as summarized in Figure 11c. However, the trend in responses suggests a layered decision-making process: while 76.4% agreed that using harvested rainwater for ablution is religiously permissible, slightly fewer respondents (73.5%) expressed personal willingness to use it, and an even lower percentage (71.1%) supported institutional adoption. This gap implies that while many accept the practice in principle, concerns related to hygiene, trust in institutional water management, or maintenance challenges may influence their support for implementation at a broader level.

Despite this, the strong level of support for institutional adoption of rainwater systems highlights the potential for mosques and religious institutions to act as catalysts for public acceptance and confidence in sustainable water practices. Such initiatives not only serve as practical demonstrations of sustainability but also align with religious practices, making them particularly resonant in culturally and spiritually significant contexts. By integrating rainwater harvesting into mosques and other institutions, opportunities arise for public education, fostering greater awareness of water conservation. This approach reinforces the alignment between religious values and sustainability while addressing community-wide water needs through tangible and visible solutions. Together, these findings highlight a strong alignment between Islamic teachings and sustainable water practices. By addressing practical concerns, such as cleanliness and theological clarity, harvested rainwater has the potential to be widely adopted for ablution, fostering conservation within the context of deeply held religious values.

4. Discussion and Limitations

Table 4. Summary of hypotheses testing and key findings for public acceptance of RWH systems and recycled rainwater applications.

Hypothesis	Support Status	Key Finding
Public Acceptance of General RWH Systems
H1: PEU → PU	Supported	Perceived ease of use (PEU) of RWH systems positively influences perceived usefulness (PU).
H2: PU → ATU	Supported	Perceived usefulness (PU) of RWH systems significantly impacts attitudes toward use (ATU).
H3: PEU → ATU	Supported	Perceived ease of use (PEU) directly improves attitudes toward using RWH systems (ATU)
H4: ATU → ITU	Supported	Attitudes toward RWH systems (ATU) strongly influence intentions to use (ITU).
H5: SK → PU	Supported	Subjective knowledge (SK) enhances perceptions of RWH system usefulness (PU).
H6: SK → ATU	Supported	Higher subjective knowledge (SK) leads to more favorable attitudes toward use (ATU).
H7: SK → ITU	Supported	Subjective knowledge (SK) positively affects the intention to use RWH systems (ITU).
H8: PC → PEU	Supported	Perceived cost (PC) negatively affects the perceived ease of use (PEU) of RWH systems.
H9: PC → PU	Rejected	Perceived cost (PC) does not significantly impact perceived usefulness (PU).
H10: PC → ATU	Supported	Higher perceived cost (PC) negatively influences attitudes toward using RWH systems (ATU).
H11: PC → ITU	Supported	Perceived cost (PC) creates a barrier to the intention to use RWH systems (ITU).
H12: TR → PEU	Supported	Higher technical requirements (TR) reduce the perceived ease of use (PEU) of RWH systems.
H13: TR → PU	Rejected	Technical requirements (TR) do not significantly affect perceived usefulness (PU).
H14: TR → ATU	Supported	Higher technical requirements (TR) negatively affect attitudes toward using RWH systems (ATU).
H15: TR → ITU	Supported	Perceived technical complexity (TR) discourages intentions to use RWH systems (ITU).
Public Acceptance of Recycled Rainwater Applications
H1: PEU → PU	Supported	Perceived ease of use (PEU) of recycled rainwater systems improves perceived usefulness (PU).
H2: PU → ATU	Supported	Perceived usefulness (PU) of recycled rainwater positively influences attitudes toward use (ATU).
H3: PEU → ATU	Supported	Perceived ease of use (PEU) enhances attitudes toward using recycled rainwater (ATU).
H4: ATU → ITU	Supported	Attitudes toward recycled rainwater systems (ATU) strongly drive intentions to use them (ITU).
H8: PC → PEU	Supported	Perceived cost (PC) negatively impacts perceived ease of use (PEU) of recycled rainwater applications.
H9: PC → PU	Supported	Higher perceived cost (PC) reduces perceived usefulness (PU) of recycled rainwater applications.
H10: PC → ATU	Supported	Perceived cost (PC) negatively affects attitudes toward using recycled rainwater (ATU).
H11: PC → ITU	Supported	Higher perceived cost (PC) lowers the intention to use recycled rainwater applications (ITU).
H16: PR → PU	Rejected	Perceived risk (PR) does not significantly influence perceived usefulness (PU).
H17: PR → ATU	Rejected	Perceived risk (PR) does not significantly affect attitudes toward using recycled rainwater (ATU).
H18: PR → ITU	Rejected	Perceived risk (PR) does not significantly deter intentions to use recycled rainwater applications (ITU).

presents a summary of the hypotheses tested under the extended TAM framework for both the general acceptance of RWH systems and the acceptance of recycled rainwater applications; highlighting the significance of each tested relationship, along with the corresponding regression results, allowing for a clearer interpretation of the factors influencing public acceptance. These findings provide valuable insights into the role of core TAM constructs, such as perceived usefulness, perceived ease of use, attitude, and intention, as well as the impact of external factors, such as perceived cost, technical requirements, subjective knowledge, and perceived risk. The subsequent discussion delves deeper into the implications of these results, identifying key barriers and facilitators to RWH adoption and offering recommendations for policymakers and stakeholders.

The findings of this study reveal that respondents generally have positive perceptions of RWH systems and recycling rainwater, despite most of them not owning such systems. The respondents’ perception of the usefulness of the system, ease of use, attitude towards its implementation, and their intentions to adopt it have a significant relationship to their acceptance of the system. External factors, such as technical requirements, perceived cost, and subjective knowledge, also shape these perceptions

A common concern among respondents was the technical requirements associated with installing and maintaining RWH systems. Similar to findings from a study conducted in Iran [30], where a lack of knowledge on the technical requirements of RWH system was reported as a significant barrier to adoption, respondents in this study also indicated that the provision of installation and maintenance services may be an effective measure to encourage adoption of the system. With 77.59% of respondents identifying technical support as a necessary initiative, this study underscores the need for relevant technical institutions to enhance their expertise in RWH systems as well as for startups to explore the installation and maintenance of RWH systems. Building public trust through accessible technical guidance and reliable maintenance services is essential to improving adoption rates.

The strongest predictor of overall acceptance of RWH systems is the perceived cost. Previous research has shown that the cost of alternative water sources, particularly municipal water, is an important factor in the acceptance of RWH system [36,37] with most respondents rightly considering RWH systems to be more expensive; a sentiment corroborated by other studies [12,37]. Based on the acceptance model, perceived cost has a direct influence on perceived ease of use, attitudes, and intentions to adopt RWH systems. Financial incentives, such as subsidies or tax reliefs, could mitigate affordability barriers and encourage broader adoption. However, this study also highlights that while subsidies are important, other initiatives, such as education and technical support, may have an even greater influence on public acceptance.

Subjective knowledge is also another significant influence on the acceptance of RWH systems. Respondents who perceived themselves to be more informed about RWH systems were more likely to view them positively, aligning with a previous study that showed that the likelihood of use increases when information is provided [38]. With 84.83% of respondents emphasizing the need for publicity and education on RWH systems, raising awareness through targeted campaigns should be prioritized. Therefore, the first step in improving the public’s perception of RWH system should be by providing clear and accessible information on the benefits and operation of RWH systems.

Interestingly, perception of risk associated with collected rainwater holds no significant value on the acceptance of RWH systems. Although some respondents expressed concerns about safety and quality, all hypotheses related to perceived risk were rejected; indicating despite the minor apprehensions, the majority of respondents were open to using rainwater for non-potable purposes, such as cleaning and irrigation, and for religious practices, such as ablution. The lack of strong perceived risk barriers suggests that other factors play a greater role in influencing public acceptance of RWH systems.

Within the context of religious practices, the use of rainwater for ablution purposes received positive responses, with 73.49% of respondents expressing willingness to use rainwater for ablution. This is indeed good news as ablution alone can account for up to 50 L per person out of the 380 L of daily water consumption in Brunei. Concerns about cleanliness were the primary reservation, echoing findings from earlier studies. However, previous research in Brunei has shown that rainwater is safe for ablution [22]. Water quality analysis from prior feasibility studies indicated that harvested rainwater in Brunei has pH values ranging between 4.11 and 6.46, which, while below the WHO-recommended drinking water standard (pH 6.5–8.5) [39], remains within acceptable limits for non-potable applications such as ablution. Furthermore, key parameters such as total dissolved solids (TDS), electrical conductivity (EC), turbidity, and dissolved oxygen (DO) were found to be well within WHO potable water limits, confirming the overall safety of harvested rainwater for ritual purification [40]. It is also important to note that rainwater has traditionally been used for ablution. Rainwater harvesting has long served as a practical and sustainable water source for religious purification. Furthermore, Islamic jurisprudence emphasizes that water must be clean and tahir (ritually pure) for ablution but does not necessarily require it to be potable. Since harvested rainwater meets the criteria of tahir water and aligns with Islamic guidelines, its use for ablution remains a valid and practical option. Given these findings, public education campaigns that highlight the quality and safety of rainwater for religious purposes are important to alleviate these concerns and further enhance acceptance on using rainwater for ablution. With strong cultural and spiritual alignment, integrating RWH systems for ablution represents a practical and symbolic step towards sustainable water management.

Despite the positive response towards using rainwater for ablution, some limitations of the study should be acknowledged. While prior studies have confirmed the safety of harvested rainwater for non-potable applications, variations in environmental conditions, collection methods, and storage practices may influence water quality, with factors such as prolonged storage, microbial growth, and potential contamination from catchment surfaces posing challenges in maintaining consistent water quality over time. Further investigations on long-term water quality monitoring and appropriate low-cost treatment methods could enhance public confidence in the system and ensure its safe use for religious and household purposes.

In addition to technical considerations, certain limitations in the study design should also be noted; the survey was conducted using a non-probability convenience sampling approach, which may have introduced demographic biases. The fact is the sample was skewed towards younger and more educated respondents, which does not fully reflect the general Bruneian population. Since age and education level can influence environmental awareness and technology adoption, the findings may not fully represent the perspectives of older generations or individuals with lower educational attainment. This discrepancy is likely due to the survey’s online distribution via WhatsApp and email, which naturally favored younger and digitally active individuals. Consequently, older individuals and those with limited digital access were underrepresented, despite Brunei’s high internet penetration rate (~99%). While the study provides useful insights from early adopters, who are often key drivers of technology adoption according to Bass Diffusion Theory, future research should incorporate more inclusive survey methods, such as in-person surveys, telephone interviews, or stratified sampling, to ensure broader demographic representation. However, such approaches would require additional resources, including time, funding, and logistical support, to effectively reach underrepresented groups. Balancing feasibility with inclusivity remains a key challenge in expanding future research on public acceptance of RWH systems.

Beyond survey limitations, future research should also expand towards pilot-scale implementation of RWH systems within different settings, such as households, commercial buildings, and religious institutions. Indeed, a pilot-scale RWH system is currently in the planning stages at the university mosque. Field studies evaluating real-world feasibility, economic viability, and operational challenges would provide deeper insights into long-term sustainability. Additionally, research into user behavior and maintenance practices would help refine strategies for promoting adoption and ensuring system longevity. Expanding the study to other predominantly Muslim countries could also provide comparative insights into cultural and regional variations in RWH acceptance for religious practices. Investigating policy frameworks, financial incentives, and institutional support mechanisms in different countries could offer best practices for effectively integrating RWH systems into national water management strategies.

A promising direction for future research is the application of Bass Diffusion Theory to model and predict the adoption of RWH systems. This theory distinguishes between innovators, early adopters, and the majority population, allowing researchers to forecast adoption trends based on public perception, policy interventions, and market dynamics. By incorporating this framework, future studies could provide data-driven predictions on how quickly RWH systems may be adopted under varying policy, educational, and financial incentive scenarios.

By addressing these limitations and extending research into practical implementation and policy development, RWH systems can be further optimized and promoted as a sustainable water conservation strategy that aligns with both environmental sustainability and religious values.

5. Conclusions

Water scarcity is a growing global concern, driven by factors such as population growth, urbanization, and the impacts of climate change. Brunei Darussalam, with high per capita water consumption rates and increasing expected water demand, is not excluded from these challenges. Rainwater Harvesting (RWH) systems offer a sustainable alternative to alleviate reliance on treated potable water while addressing environmental and societal needs. However, our previous techno-economic analysis of RWH systems in Brunei highlighted significant economic barriers, showing that subsidies are essential to enhance the feasibility and affordability of such systems for widespread adoption, mostly due to the cheap price of municipal water in Brunei.

This study expanded on previous work by assessing public acceptance of RWH systems and recycled rainwater applications using an extended Technology Acceptance Model (TAM) framework. The model evaluated core TAM constructs: Perceived Ease of Use (PEU), Perceived Usefulness (PU), Attitude Towards Use (ATU), and Intentions to Use (ITU), as well as external factors, including Subjective Knowledge (SK), Perceived Cost (PC), Perceived Risk (PR), and Technical Requirements (TR). Data from survey questionnaires were analyzed using regression analysis to identify significant relationships and predictors of public acceptance. The findings revealed strong support for the core TAM relationships, validating the framework for both general RWH systems and recycled rainwater applications. PEU significantly influenced PU, and both PEU and PU emerged as strong predictors of ATU. ATU demonstrated the strongest predictive power, directly influencing ITU and accounting for a substantial proportion of the variance in behavioral intentions. The extended framework highlighted the critical role of external factors. SK positively influenced PU and ITU, suggesting that familiarity with RWH systems enhances acceptance. PC and TR, while posing barriers, significantly influenced PEU, ATU, and ITU, underscoring the need for financial incentives and technical support to foster adoption. On the other hand, PR did not exhibit significant effects on acceptance, indicating general public confidence in the safety of recycled rainwater for non-potable applications.

This study also explored the public’s perceptions of initiatives to promote RWH systems. Publicity and education were identified as the most critical measures, selected by 84.83% of respondents, reflecting the importance of addressing knowledge gaps. Installation and maintenance services, as well as technical guidance, were also highlighted as pivotal for facilitating adoption. Financial incentives, such as subsidies, were recognized as important but ranked lower than education and technical support. Collectively, these suggest that a multifaceted approach is necessary to improve adoption.

For recycled rainwater applications, the findings emphasized strong public recognition of the benefits, particularly in terms of water conservation and reducing dependence on municipal water supplies. While concerns regarding water quality and safety are important barriers for those with a negative or uncertain attitude towards RWH, they do not appear to be significant obstacles for the majority of the respondents. Generally, Muslim respondents expressed a generally positive attitude toward using rainwater for ablution, with 73.49% willing to adopt the practice. However, concerns about cleanliness persist, underscoring the need for target initiatives to enhance trust and acceptance of rainwater for both non-potable and religious purposes.

This study offers significant insights for policymakers and relevant authorities in Brunei and beyond. By addressing cost and technical barriers, enhancing public awareness, and leveraging the positive perceptions of RWH systems, sustainable water management practices can be effectively promoted. These findings align with global Sustainable Development Goals (SDGs), particularly SDG 6 (Clean Water and Sanitation), SDG 12 (Responsible Consumption and Production), and SDG 13 (Climate Action). Implementing these strategies can drive the adoption of RWH systems, contributing to water security, sustainability, and resilience in the face of growing environmental challenges.

While the findings are specific to Brunei, they hold broader relevance for other regions facing water sustainability challenges, particularly those with high rainfall, cultural or religious drivers for water use, and reliance on municipal water supplies. The methodology adopted in this study provides a replicable framework for assessing public acceptance of RWH systems and can be applied in other countries to inform localized policy interventions. For predominantly Muslim countries, where ablution is an essential practice, integrating RWH can serve as both a water conservation strategy and a culturally relevant sustainability initiative. However, regional differences in climate, infrastructure, water governance, and public perceptions should be considered when applying these insights elsewhere. Future cross-regional studies would provide valuable comparative perspectives and help refine best practices for scaling up RWH adoption globally. By fostering collaborations between researchers, policymakers, and institutions, RWH can be further optimized as a viable, sustainable, and culturally inclusive water management solution.