Cath Hassell | ech2o
Anyone who is used to working in the commercial sector and looking at scoring easy BREEAM points will already know all about total washroom control (1). For the rest of you think urinal controls only bigger, better, faster, exerting control over all the water supply into a toilet block.
Benchmarking of schools
The main way of comparing different buildings with regards to how much water they use is based on the number of building users. For schools the measurement is m3/pupil/year which allows us to compare different sized schools quickly and easily. The figures we use to benchmark schools against are taken from 2005-6 data 3 survey of 14,000 schools across England and Wales (2). On average primary schools without a pool use 5.2 m3/pupil/year and those in the best performing 25% use 3m3/pupil/year. The corresponding figures for secondary schools are 4.4m3/pupil/year on average and 2.6m3/pupil/year for the top quartile.
Part of ech2o’s work involves analysing school water consumption and we rarely find a school that performs better than the average. We also know that most schools that are using the average amount of water per pupil either have uncontrolled urinal flushing or other reasons for unexplained water use when the school is shut. One secondary school we benchmarked at below average use (at 3.8m3/pupil/year check this figure) not only had uncontrolled urinals, but leaking pipes in the boys toilets and push taps that failed to switch off in both the girls and boys toilets. So obviously the typical school usage of water figure can hide a multitude of sins…
If we unpick the yearly figures a bit and recognise that schools are only open (or at least filled with pupils) 200 days a year, the average primary school pupil uses 26 litres of water a day. At first glance that doesn’t seem so bad. After all the average water consumption per day in dwellings in the UK is 150 litres of water. But, at schools there is no bathing. So, in the main, water use is restricted to flushing toilets and urinals, washing hands, and in the canteen. Given that most boys will be using the urinal rather than WC while at school, then we see that 26 litres of water per pupil per day is far too high.
5.2m3 of water at current prices costs between £11 to £31 depending on where in the UK the school is situated (3). Using those figures, a single form entry primary school with reception class will have 210 pupils and a water bill of £2,310 – £6,497. If the school reduces their water use to 3m2/pupil/year (by a combination of water efficiency upgrades and behaviour change) then the cost falls to £1,317 to £3,749. This is a saving of £993 to £2,748 respectively a year. Corresponding costs in larger primary schools (many of which are now two form entry) and secondary schools (over 50% of which have more than 1,000 pupils (4)) will be greater, as will potential savings.
School water audits and upgrades
Currently, water audits and water efficiency retrofits concentrate on urinal controls and dual flush mechanisms or save-a-flush bags for toilet cisterns. If taps are controlled by turning on or off then some retrofits include changing the mechanism to push type taps. But these solutions fail to address all of the reasons for water wastage in schools. The deliberate leaving on of taps, young children forgetting to turn taps off after use, failing push taps that remain stuck in the ‘on’ position, and WC leakage – whether through ball valves that fail to shut off or faulty flush mechanisms letting by, all contribute to unnecessary water use. By controlling all the water supply into the toilet block, all of the above will still cause wastage of water, but the amount of time in which they do so will be reduced dramatically.
How does total washroom control work?
Total washroom control consists of a PIR (passive infra-red) device that picks up occupancy within the area it controls. When the system detects a user entering the room it activates a solenoid valve or valves (hot, cold or rain/grey water supplies) to allow water to flow freely to all appliances. If no motion is detected after a set amount of time (usually 15 or 30 minutes), the valve will close the water supply to the area until further movement is detected. The PIR sensor is ideally located at the entrance to the toilet block and the solenoid valve(s) should be located as close as possible to where the piped supplies enter the room. As with urinal controls, there is a hygiene flush which is usually timed to operate once every 24 hours if no occupancy has been detected and systems are low voltage so little energy is required to operate them.
As with most things, they are easy to design into a new build situation and harder to retrofit. But that shouldn’t stop the potential for total washroom control to be considered in every school water efficiency audit. Prices start at £369 for one sensor control and 22mm valve so controlling both hot and cold water can cost up to £700 plus fitting, which is more expensive than standard urinal controls which usually cost about £220 to fit per unit. The standard configuration of pipework to automatic flushing cisterns means that urinal controls are usually easy to retrofit, whereas total washroom controllers may be more difficult as the pipework is likely to be hidden in the roof void. But if it is possible, it should be done. Of course it won’t prevent loo paper ceiling bombs or graffiti on the back of toilet doors, and taps should still be maintained and faulty ball valves and flushing valves replaced. But with the ability to eliminate the risk of flooding due to accidental or deliberate vandalism (that time honoured trick of blocking the washbasins with paper towels and leaving the taps running) and water wastage due to defective taps, valves etc., specifying total washroom control is an excellent solution, especially once more than one urinal control is required.
This blog was first published in Green Building Magazine, Winter 2014 edition4
(1) To gain the credit under BREEAM Wat 4 evidence must be provided to demonstrate that proximity detection shut off is provided to the water supply to all urinals and WCs.
(2) Department for Education, ‘School and college performance tables’
http://www.education.gov.uk/performancetables/, (now archived)
(3) £2.09/m3 in Thames Water area (the cheapest of the main water and sewerage providers to £5.95/m3 in South West Water area (the most expensive).