Saving water in businesses and schools – urinal flush control valves
Uncontrolled urinal flushing can easily account for most of the water used in public and commercial buildings. Fitting flush controllers overcomes this problem. It is an option that can be a cost effective solution for reducing the amount of water used.
Many urinal installations do not have controls and so flush continuously, and often at a higher rate than specified by the regulations.
For an office with a 40-hour working week this means that 76 per cent of the flushing occurs when the building is unoccupied.
Under the Water Regulations, urinals should use no more than 7.5 litres per bowl per hour (10 litres for a single bowl) and should have a device fitted to prevent flushing when the building is not being used. In practice, flow rates are rarely measured and will drift with time, or are deliberately increased in a usually vain attempt to solve odour problems.
Many designs of flush controller are available. These either use a timer to match the hours of use or detect the presence of people. This is typically achieved by means of infrared movement detectors or door switches. Mechanical designs use water flow or variations in pressure caused by taps being used, to open a valve to the urinal cistern.
Some controls allow the urinal cistern to fill slowly unless no activity has been detected for a preset period. Other designs allow the cistern to fill quickly, causing it to flush when people are detected. An electronic delay prevents further flushing for a preset period. Each method has its advantages.
Where a large number of urinals are installed with a quick-fill system, separate controllers may be needed to prevent all the bowls flushing when one person enters the room.
Whatever system is installed, it must be correctly set up, tested and maintained.
Monitoring at Worthing High School found the urinals were responsible for over 40 per cent of the schools total water use. This rose to 80 per cent as the trial progressed. The problem was traced to faulty urinal controllers, and the situation might have continued undetected had the school not been carrying out a detailed water audit.
The same circuitry can control lights and shut off the water supply when the washroom is unoccupied, therefore saving energy as well as water.
Chesswood Middle School saved nearly 900m3 per year (a 68 per cent reduction in the total amount of water used by the school) by fitting urinal flush controllers. Urinal flush controllers proved to be the most cost effective of a range of water efficiency measures installed throughout the school.
Water use due to urinals 1,314m3 per year
After fitting controllers 419m3
Water saved 895m3
Money saved £1,414 per year
Cost of installation £960
Payback: around eight months