W02: Low Flow Faucets for Waterbasins

Requirement Summary

Savings can be achieved if the flow rate of the faucets specified for the washbasins in the building are less than the base case in liters per minute. This low flow rate must be obtained through the use of aerators and auto shut off controls.

Intention

By specifying aerators and auto shut-off faucets for washbasins and sinks, water use is reduced without adversely affecting functionality.

Approach/Methodologies

As the flow rate of a faucet is dependent on the water pressure, manufacturers often provide a chart that plots the flow rate at different pressures. To improve consistency, the flow rate used for the EDGE assessment in the design/pre-construction phase must be that quoted for the operating pressure of 3 bar (43.5 psi). At the post-construction stage, actual flow rates must be used. If this flow rate is not available, physical measurements can be made on site using a bucket of a known size and a timer to record the flow rate. Multiple measurements must be made across a variety of locations and floors to come up with a weighted average.

If the measure is claimed, then the assumed improved flow rate is 2 liters per minute. If the flow rate is greater than 2 liters per minute but lower than the baseline in liters per minute, the measure can still be claimed if the actual flow rate is entered. The lower the flow rate the greater the water savings.

Potential Technologies/Strategies

This measure includes two technologies fitted to the faucet – aerators and auto shut-off valves – which must be purchased as one product.

Aerators are small water-saving devices attached to the faucet that maintain user satisfaction at the lower flow rates. They mix water with air to cause turbulence in the flow; this in turn gives an increased sense of pressure without increasing the flow rate. They are also called flow regulators.

Auto shut-off faucets are activated by a push action or electronic sensors that allow the water flow to last for a programmed length of time, usually 15 seconds. After this period the faucet shuts off automatically, which is ideal for public and unsupervised washing areas.

Flow restrictors or aerators can be added on to the specified faucets to reduce the flow rate, which may be a cheaper alternative to purchasing a low-flow faucet.

Relationship to Other Measures

Reducing the flow rate of all the washbasin faucets in the building reduces the water demand and the energy required to produce hot water for the faucets.

Assumptions

The base case assumptions vary by location. Globally, the typical baseline flow rate is 6 liters per minute for all the faucets in all the washbasins; it is assumed that these faucets do not have auto shut-off technology. The improved case has aerated, auto shut-off faucets with a default flow rate of 2 liters per minute in all the washbasins included in the measure.

Compliance Guidance

Design Stage	Post-Construction Stage
At the design stage, the following must be used to demonstrate compliance:  Plumbing drawings/specifications including make, model auto shut-off mechanism and flow rate of the washbasin faucet(s); or  Manufacturer’s data sheet for faucet(s)/flow aerator(s) confirming the flow rate at 3 bar.	At the post-construction stage, the following must be used to demonstrate compliance: On-site test results by the auditor of the flow rate at the highest flow per minute, using a timer and a measurement container; and Photographs of the installed faucet(s); or  Purchase receipts and delivery note for faucet(s) which includes make, model and auto shut-off mechanism.

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