W06: Low Flow Pre-Rinse Spray Valves for Dishwashing – Above Green

Requirement Summary

This measure can be claimed if the kitchens are fitted with low flow pre-rinse spray valves for rinsing the dishes prior to be placed in the washing machine. The pre-rinse valve specified should be 6 liters per minute or less.

Intention

By specifying low-flow pre-rinse valve, water use is reduced compared to a manual rinse of the dishes.

Approach/Methodologies

As the flow rate of the pre-rinse valve is dependent on the water pressure, manufacturers often provide a chart that plots the flow rate at different pressures. In order 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 on site must be used for the EDGE inputs. If the flow rates of the spray valves vary across a project, a weighted average must be used.

Some of the benefits of having an efficient pre-rinse valve in the kitchen of the hospital include having an efficient cleaning but using less water and energy, which then reduce the operational costs.

Potential Technologies/Strategies

Many different pre-rinse valves are available in the market; however as the flow rate required is low, efficient spray valves need to meet 6 liters per minute flow rate. In order to maintain user satisfaction at the lower flow rates, manufacturers mix water with air to cause turbulence in the flow; this in turn gives an increased sense of pressure without increasing the flow rate. Pre-rinse spray valves require a lot of pressure, which is given by the air within the valve, to remove the food waste prior to dishwashing. The savings are even more noticeable because pre-rinse valves use hot water, so when water is reduced the use of energy is also dropped.

Relationship to Other Measures

Water reduction in the 'Kitchen' section of the water chart is expected by low flow pre-rinse valves. Moreover, it shows reductions in energy due to 'water heating' and water pumps which is part of 'Others'.

Assumptions

The base case assumption is a flow rate of 19 liters per minute and the improved case default is a flow rate of 6 liters per minute.

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, and flow rate of the pre-rinse valve(s); or
Manufacturer’s data sheet for pre-rinse valve(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 pre-rinse valve(s); or
Purchase receipts and delivery note for pre-rinse valve(s).