Investigations on the Influence of Total Water Hardness and pH Value on the Measurement Accuracy of Domestic Cold Water Meters
Abstract
:1. Introduction
2. Background
2.1. Cold Water Meters
2.2. Water Quality Parameter: pH Value
2.2.1. Low pH Value
2.2.2. High pH Value
2.3. Water Quality Parameter: Hardness
2.3.1. Low Hardness (Soft Water)
2.3.2. High Hardness (Hard Water)
3. Boundary Conditions and Procedure
3.1. Accelerated Wear Test
3.2. Water Meter Calibration—Before and after
3.3. Test Conditions of the Accelerated Wear Test
3.3.1. Water Temperature
3.3.2. Flow Rate and Pressure
4. Test Water Preparation
4.1. pH Value Experiments
- pH value low: pH ;
- pH value medium: pH ;
- pH value high: pH .
4.2. Hardness Experiments
- Hardness low (soft water): less than mmol −1 calcium carbonate;
- Hardness medium: 1.5 mmol −1 to 2.5 mmol −1 calcium carbonate;
- Hardness high (hard water): more than mmol −1 calcium carbonate.
- Hardness low: 1 mmol −1 calcium carbonate ( );
- Hardness medium: 2 mmol −1 calcium carbonate ( );
- Hardness high: 3 mmol −1 calcium carbonate ( ).
4.3. Chemicals
4.4. Base Model Water (MW)
4.5. Highly Purified Water (HPW)
4.6. Test Waters
5. Measurement Set-Up
5.1. Calibration Facility
5.2. Accelerated Wear Test facility
5.2.1. Operating Principle
5.2.2. Acquired Measurement Data
- (a)
- Temperature compensated pH value measurements in a range from 0 to 14; resolution: pH ; accuracy: pH ;
- (b)
- Temperature compensated water hardness measurements in a range from 0.1 to 40 ; resolution: (optional: ); accuracy: ±5%);
- (c)
- Temperature compensated conductivity measurements in a range from 0 cm−1 to 2000 cm−1; resolution: 1 cm−1; accuracy: below ±1%.
- (a)
- pH Value Sensor
- (b)
- Hardness Sensor
- (c)
- Conductivity Sensor with in-Built Temperature Sensor
6. Measurement Results
6.1. Calibration of the Water Meters before the Wear Test
- Flow rate: to 1.1 ;
- Flow rate: to 1.1 ;
- Flow rate: 0.33 ( + ) to 0.37 ( + );
- Flow rate: 0.67 ( + ) to 0.74 ( + );
- Flow rate: 0.9 to ;
- Flow rate: 0.95 to .
6.1.1. Multi-Jet Cold Water Meters (B Meters)
6.1.2. Ultrasonic Cold Water Meters (Kamstrup)
6.2. Accelerated Wear Tests
6.2.1. pH Value Measurements
6.2.2. Total Hardness Measurements
6.2.3. Conductivity Measurements
6.3. Re-Calibration of the Water Meters after the Wear Test
6.3.1. Multi-Jet Cold Water Meters (B Meters)
6.3.2. Ultrasonic Cold Water Meters (Kamstrup)
7. Conclusions and Discussion
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
Abbreviations
ASTM | American Society for Testing Materials |
CMI | Czech Metrology Institute |
DIN | Deutsche Industrienorm (German Institute for Standardization) |
DVGW | Deutscher Verein des Gas- und Wasserfaches e.V. (German Technical and Scientific Association for Gas and Water) |
EC | European Commission |
EEC | European Economic Community |
EMC | Electromagnetic Compatibility |
EMPIR | European Metrology Programme for Innovation and Research |
FNU | Formazin Nephelometric Unit |
HPW | Highly Purified Water |
IMD | Individuell mätning och debitering (Individual metering and billing) |
ISO | International Organization for Standardization |
JRP | Joint Research Project |
MID | Measuring Instruments Directive |
MPE | Maximum Permissible Error |
MW | Model Water |
NMI | National Metrology Institute |
OIML | International Organization of Legal Metrology |
PTB | Physikalisch-Technische Bundesanstalt (The National Metrology Institute of Germany) |
QMS | Quality Management System |
RISE | Research Institutes of Sweden |
SL | Stock Solution |
TZW | DVGW-Technologiezentrum Wasser (German Water Centre) |
VM7 | Vattenmätbänk no. 7 (calibration facility at RISE) |
WELMEC | Western European Legal Metrology Cooperation |
WRMG | Wasch- und Reinigungsmittelgesetz (Washing and Cleaning Agents Act) |
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ISO 4064 (Old) Earlier Version of ISO 4064 | MID (New) Current Version of ISO 4064 | |
---|---|---|
Nominal flow rate; given value | (n or N: meter designation) | |
(Permanent flow rate ) | ||
Measuring range; given value | to (); depending on | R with: R ≥ 40 |
the metrological class A, B or C | ||
Minimum flow rate | ; depending on the metrological class | with: |
() | = with: (class A), | |
(class B), (class C) | ||
Transitional flow rate | ; depending on the metrological class | with: |
() | = with: (class A), | |
(class B), (class C) | ||
Maximum flow rate | with: | with: |
(Overload flow rate ) | ||
Maximum Permissible Error | to : ±5% | to : ±5% and |
(MPE) | to : ±2% | to : ±2% |
Water Meter Size | Number of Residential Units |
---|---|
Flat water meter (individual level, 1 residential unit) | |
House water meter: 1 to 30 residential units | |
House water meter: 31 to 200 residential units | |
House water meter: 201 to 600 residential units |
Chemical Name | Chemical Formula | CAS Number |
---|---|---|
Calcium chloride | CaCl2 × 2H2O | 10035-04-8 |
dihydrate | ||
Magnesium sulfate | MgSO4 × 7H2O | 10034-99-8 |
heptahydrate | ||
Sodium bicarbonate/ | NaHCO3 | 144-55-8 |
Sodium hydrogen | ||
carbonate | ||
Di-Sodium hydrogen | Na2HPO4 × 2H2O | 10028-24-7 |
phosphate dihydrate | ||
Potassium dihydrogen | KH2PO4 | 7778-77-0 |
phosphate | ||
Sodium hydroxide | NaOH | 1310-73-2 |
Chemical Name | Concentration SL g L | Ion | Ion Concentration in SL g L | SL Dosing mL (SL)/L (MW) | Concentration MW mg L |
---|---|---|---|---|---|
Calcium chloride | Cl− | 41.9 | 21.0 | ||
dihydrate | 86.9 | Ca2+ | 23.7 | 0.5 | 11.8 |
Magnesium sulfate | SO42− | 30.4 | 60.7 | ||
heptahydrate | 77.9 | Mg2+ | 7.7 | 2.0 | 15.4 |
Sodium | |||||
bicarbonate | 67.2 | HCO3− | 48.8 | 2.5 | 122.0 |
Chemical Name | Concentration SL g L | Ion | Ion Concentration in SL g L | SL Dosing mL (SL)/L (MW) | Concentration MW mg L |
---|---|---|---|---|---|
Calcium chloride | Cl− | 41.9 | 44.6 | ||
dihydrate | 86.9 | Ca2+ | 23.7 | 1.064 | 25.2 |
Magnesium sulfate | SO42− | 30.4 | 129.3 | ||
heptahydrate | 77.9 | Mg2+ | 7.7 | 4.256 | 32.7 |
Sodium | |||||
bicarbonate | 67.2 | HCO3− | 48.8 | 2.5 | 122.0 |
Chemical Name | Concentration SL g L | Ion | Ion Concentration in SL g L | SL Dosing mL (SL)/L (MW) | Concentration MW mg L |
---|---|---|---|---|---|
Calcium chloride | Cl− | 41.9 | 68.4 | ||
dihydrate | 86.9 | Ca2+ | 23.7 | 1.632 | 38.7 |
Magnesium sulfate | SO42− | 30.4 | 198.2 | ||
heptahydrate | 77.9 | Mg2+ | 7.7 | 6.526 | 50.1 |
Sodium | |||||
bicarbonate | 67.2 | HCO3− | 48.8 | 2.5 | 122.0 |
Chemical Name | Concentration SL g L | Ion | Ion Concentration in SL g L | SL Dosing mL (SL)/L (MW) | Concentration MW mg L |
---|---|---|---|---|---|
Calcium chloride | Cl− | 41.9 | 21.0 | ||
dihydrate | 86.9 | Ca2+ | 23.7 | 0.5 | 11.8 |
Magnesium sulfate | SO42− | 30.4 | 60.7 | ||
heptahydrate | 77.9 | Mg2+ | 7.7 | 2.0 | 15.4 |
Sodium | HCO3− | 48.8 | 122.0 | ||
bicarbonate | 67.2 | Na+ | 18.4 | 2.5 | 46.0 |
Di-Sodium hydrogen | |||||
phosphate dihydrate | – | – | – | – | 1370.0 |
Potassium dihydrogen | |||||
phosphate | – | – | – | – | 3340.0 |
Chemical Name | Concentration SL g L | Ion | Ion Concentration in SL g L | SL Dosing mL (SL)/L (MW) | Concentration MW mg L |
---|---|---|---|---|---|
Calcium chloride | Cl− | 41.9 | 21.0 | ||
dihydrate | 86.9 | Ca2+ | 23.7 | 0.5 | 11.8 |
Magnesium sulfate | SO42− | 30.4 | 60.7 | ||
heptahydrate | 77.9 | Mg2+ | 7.7 | 2.0 | 15.4 |
Sodium | |||||
bicarbonate | 67.2 | HCO3− | 48.8 | 2.5 | 122.0 |
Di-Sodium hydrogen | |||||
phosphate dihydrate | – | – | – | – | 1443.0 |
Potassium dihydrogen | |||||
phosphate | – | – | – | – | 258.0 |
Chemical Name | Concentration SL g L | Ion | Ion Concentration in SL g L | SL Dosing mL (SL)/L (MW) | Concentration MW mg L |
---|---|---|---|---|---|
Calcium chloride | Cl− | 41.9 | 21.0 | ||
dihydrate | 86.9 | Ca2+ | 23.7 | 0.5 | 11.8 |
Magnesium sulfate | SO42− | 30.4 | 60.7 | ||
heptahydrate | 77.9 | Mg2+ | 7.7 | 2.0 | 15.4 |
Sodium | |||||
bicarbonate | 67.2 | HCO3− | 48.8 | 2.5 | 122.0 |
Sodium | |||||
hydroxide | 80.0 | – | – | 0.17 | – |
Parameter | Specification |
---|---|
Measuring method | Volumetric (prover or master meter) |
Medium | Water |
Flow rate | 0.1 −1 to 100 −1 |
6 −1 to 6000 −1 | |
Temperature | 5 to 90 |
Pressure | Up to |
Measurement uncertainty | U |
1. Hardness | 2. Hardness | 3. Hardness | 4. pH Value | 5. pH Value | 6. pH Value | |
---|---|---|---|---|---|---|
Low | Medium | High | Low | Medium | High | |
Target values | ||||||
pH value | – | – | – | 6.50 | 7.70 | 9.50 |
Hardness () | 5.6 | 11.2 | 16.8 | – | – | – |
Measured values | ||||||
pH values mean | 7.87 | 7.65 | 7.66 | 6.49 | 7.69 | 9.50 |
pH values Std Dev | 0.11 | 0.03 | 0.02 | 0.04 | 0.07 | 0.04 |
Hardness mean () | 5.3 | 11.0 | 16.7 | 5.7 | 5.8 | 5.6 |
Hardness Std Dev | 0.5 | 0.5 | 0.5 | 0.3 | 0.4 | 0.2 |
Conductivity mean ( cm−1) | 380.6 | 571.4 | 752.5 | 2660 | 1684.7 | 501.3 |
Conductivity Std Dev | 1.1 | 2.1 | 3.9 | 0 | 6.6 | 25.2 |
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Büker, O.; Stolt, K.; Kroner, C.; Benkova, M.; Pavlas, J.; Seypka, V. Investigations on the Influence of Total Water Hardness and pH Value on the Measurement Accuracy of Domestic Cold Water Meters. Water 2021, 13, 2701. https://doi.org/10.3390/w13192701
Büker O, Stolt K, Kroner C, Benkova M, Pavlas J, Seypka V. Investigations on the Influence of Total Water Hardness and pH Value on the Measurement Accuracy of Domestic Cold Water Meters. Water. 2021; 13(19):2701. https://doi.org/10.3390/w13192701
Chicago/Turabian StyleBüker, Oliver, Krister Stolt, Corinna Kroner, Miroslava Benkova, Jan Pavlas, and Veit Seypka. 2021. "Investigations on the Influence of Total Water Hardness and pH Value on the Measurement Accuracy of Domestic Cold Water Meters" Water 13, no. 19: 2701. https://doi.org/10.3390/w13192701