Quantifying the Benefits of Residential Greywater Reuse

There is paucity of data on the quantification of the benefits of residential greywater reuse via direct diversion. While estimates have been made based on modelling the potential mains water savings, it is also recognised that the practicalities of system operation and occupant behaviour introduce substantial variation to these estimates. Three single residential housing projects in Fremantle, Western Australia, undertaken over ten years with a substantial focus on water efficiency and mains water substitution, have provided an opportunity to quantify these benefits. All three dwellings were intensively metered and documented. This paper describes the learnings generated along the way, including the methodology developed to effectively integrate direct diversion greywater reuse into a productive garden, along with other water sources to satisfy landscape water demand. Importantly a robust quantification of actual greywater volumes and associated mains water savings was made. The publication of actual greywater volumes will significantly contribute to this field and go a long way towards validating the merits of residential greywater reuse on mains water savings when systems are properly installed and operated. Brief considerations are also provided for energy efficiency and financial assessment.