Water efficiency measures flushed down the pan


In Water efficiency

Questions are being raised by BBC Radio 4 and The Guardian newspaper around the efficiency of dual flush toilets, as Thames Water warns that they waste more water than they conserve.

In theory, dual flush cisterns save nearly half the water per flush compared to the siphon systems they replaced – with options (on average) for a four-litre flush to remove liquid waste or a six-litre flush for solid waste. However, dual flush toilets are more prone to leaks, causing toilets to continuously flow.

The problem arises in the design. While the old style siphon cisterns used more water to flush, they were far more reliable. Designed to push water upward, the siphon works when the flush handle forces water over a lip, and down into a tube linked to the pan. Water's only way out of a siphon cistern is up.

Alternatively, dual flush toilets use a drop valve system. The drop valve is immersed in water as it sits at the bottom of the cistern. It opens to allow water out when the cistern is flushed. However, as it sits at the bottom, it is left prone to leaks as debris can block the valve from fully closing. If the valve is blocked, water is free to run from the cistern into the bowl. Therefore it’s important that households are aware of common problems with drop vales, so that they are regularly checked and maintained to ensure the system is working correctly.

Both Tom Heap for BBC and Kevin Rawlinson from The Guardian, have quoted Andrew Tucker, Water Efficiency Manager at Thames Water, discussing water loss. In his BBC interview Andrew said, "Because we've got so many [loos] that continuously flow all through the day, collectively that water loss is now exceeding the amount of water they should be saving nationally."

"The volume of water loss is getting bigger every day as more people refurbish and retrofit their older toilets and as we build more homes, so we're actually adding a problem."

Waterwise estimates that approximately 400m litres of water leak from UK toilets every day. With the issues with leaks from duel flush toilets rising, it seems the solution to water efficiency has made the situation worse.

But why is it such a problem? Surely our wet UK climate means we have water to waste? Sadly, the answer is no. Less than 3% of the Earth’s water is fresh water, the remaining 97% is salt water, which is not suitable for use in water supplies. Therefore, with a growing population, even countries surrounded by water and with damp, wet weather will still be hit by fresh water shortages.

In fact, Sir James Bevan, head of the Environment Agency has frequently stated that within 25 years, England will not have enough water to meet demand. If we continue to waste and use water at the current rate, by 2050 water shortages are set to be UK wide.

The average person currently uses around 140 litres of water a day and this number needs to reduce to 100 litres to have a meaningful impact on future shortages. Fixing leaky toilets could go a long way according to Waterwise by contributing, “Around 10% of the additional water capacity needed to cope with an extreme drought in England by 2050”.

So if you have a leaky loo, its time to call in your professional plumber. If you need to find an engineer in your area, use our online find a plumber tool.


Read the BBC and Guardian articles, featuring CIPHE Industrial Associate Thomas Dudley Ltd below:

BBC: The water-saving device wasting billions of litres every week

The Guardian: Dual-flush toilets 'wasting more water than they save'