The innovation was supposed to save us water. But now, in shocking commode news, the water-saving organization Waterwise has revealed that dual-flush toilets actually waste water. Waterwise estimates that between 5% and 8% of U.K. toilets are leaking a total of 88 million gallons per day.

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Dual-flush toilets allow users to select from a small flush for liquids and a larger flush for solid waste, a design intended to save water. This type of toilet usually depends on a drop-valve system. The valve sits underwater and opens for a flush. But debris can catch in the valve, resulting in leaks and constant running.

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“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,” Andrew Tucker, water efficiency manager at the U.K. sewerage company Thames Water, told the BBC. “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.”

Some experts say the solution is to manufacture more dual-valve toilets that use a siphon system rather than a drop valve. The siphon works by forcing water down through a tube and into the pan when you depress your toilet handle. That way, the water can only escape if it’s above the water line, which makes it much less likely to leak.

Jason Parker, managing director of U.K. plumbing manufacturer Thomas Dudley Ltd, wants drop valves outlawed, no matter the cost to his own business. “If we’re serious about wasting water and we want to stop it, the only way to do that is put a siphon back in,” he told the BBC.

Additional water is lost when dual-flush users get confused over which button to push. Thames Water’s recent consumer research found that as many as 50% of customers either chose the wrong button or pushed both.


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