Leaky Loos

Cath Hassell | ech2o 

The 1999 Water Regulations (2000 Water Byelaws in Scotland) state that ‘all WC flushing cisterns should be provided with a connection for a warning pipe, the outlet of which is to discharge in a prominent position’ and that ‘an internal overflow discharging into the WC pan shall be deemed to meet the requirements of the Regulations’.

Before 1999 any overflow from a toilet had to terminate in an obvious place and internal overflows were very much not allowed. Whilst this did not guarantee any ballvalve failure would be fixed promptly, building owners definitely had more of an incentive to do so as the damage to the external fabric of the building could be severe. Indeed, back in the 1980’s it was common to install overflows to cause an actual nuisance so terminations over front or back doors or into the overflow of a bath were often seen. 

Anyway, that has all changed. The tell-tale sign of a wet wall underneath a dripping overflow pipe has now been replaced by a film of water running down the back of a pan, something that is far harder to spot, and, even if noticed, will not be causing any damage, leading to little urgency to repair. And yet a failing ballvalve has the potential to waste significant amounts of water. In a recent trial of smart meters in 4,100 homes in south London, Thames Water found that 5% of homes had a constant stream of water into the WC pan aka a Leaky Loo, and 90% were from failing ballvalves, not, as might be expected, from failing flush valves. 

The headline figure used by most water companies for a Leaky Loo is 400 litres of water wasted per day. This is a staggering 146m³ of water a year. 400 litres a day is a 0.28 litres per minute, but my concern is that this figure is too high in the vast majority of cases where a WC is ‘leaking’. There is a huge difference in the amount of water wasted by a seeping overflow (12 litres/day compared to a WC filling up and overflowing at a rate of two or more litres/minute (something I have seen from three internal overflows in the last few months) which is 2,880 litres every 24 hours! This has two knock on effects. Headline figures of water saved that bear little resemblance to reality and an over estimation of the amount of water saved by fixing the ‘leak’ leading to misplaced use of resources.

When flush valves were first installed in the UK (back in 2001) there were quite a few high profile cases where they failed right from the start because site debris had fallen into the cisterns during installation preventing complete closure, but this situation occurs rarely now. The flap type of flush valve are particularly prone to not reseating properly, and I would like to see this type banned for use in the UK. But most flush valves won’t fail until after many years of service when the valve washer becomes brittle and starts letting by, at which point it can be replaced. Of course, there is the issue of small bright green tropical frogs that have climbed up the flush pipe from the WC pan into the cistern, who, when the loo is flushed manage to just stop themselves from being swooshed back into the pan, only for the valve to spring down and crush them resulting in a dead frog and a Leaky Loo. Though to be fair that’s not really a UK problem!

There are many reasons why a ballvalve starts to let by. As washers age they fail to shut off the incoming flow of water completely. But what is of more concern are ballvalves that are incorrectly adjusted when installed; adjusted properly but the locking nut not tightened; adjusted at some later point to “make the flush more effective"; or a WC connected directly to the incoming mains supply (high pressure) with a ballvalve orifice for a low pressure supply. 

Concealed cisterns means it’s often less straightforward to diagnose and rectify a Leaky Loo. Luckily there are cisterns that are easy to access. I was in a school recently where the WC I used was actually gushing as opposed to merely leaking. Because it was an internal overflow into the WC pan it wasn’t causing a nuisance and presumably hadn’t been reported. The school used a staggering 20m³ of water/pupil/year - a massive overuse of water as a typical primary school uses 3.8m³/pupil/year. We had assumed the issue was uncontrolled urinals and underground leakage. That proved to be correct but this was obviously adding to it. I fixed the problem there and then (a brand new ballvalve had been installed but not adjusted to cut off at the correct fill level) and calculated that this single failing ballvalve would waste 1,051m³ a year if I hadn’t fixed it - 4.7m³/pupil/year!

Thames Water are planning to produce a video about Leaky Loos, showing what one is, the various amounts of water (and money) that different flow rates will waste, the causes, and the solutions.  This is definitely to be welcomed. The more information out there with correct figures the better. And now you’d better go and check your own WC!

Comments

Many thanks Cath - more telling points presented with wit!
I thought we were doing so well recycling 5 wc suites from one refurbished building project to our own - but have already replaced 2 of the concealed cisterns and 2 of the remaining ones have intermittently leaking valves. I am reminded of all those plumbers' sharp intakes of breath when we specify anything re-used!

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