Dual-Flush Retrofit Kits: Do Their Claims Hold Water?


The recent popularity of water saving, dual-flush toilets has inspired several models of “retrofit” kits, which purport to be able to convert standard toilets (which can use up to 5 gallons of water per flush) to dual-flush by allowing homeowners to choose between a full flush or a half flush, meant to handle liquids only. The desire to conserve water is always a good thing, but the Professor couldn’t help wondering if the claims made by the manufacturers hold water or if consumers would end up flushing their money – not to mention their water savings – down the dual-flush toilet.

After doing some research into the matter, the Professor is not particularly optimistic about these devices. There is currently no independent evidence that these retrofit kits will actually save any water and they may even end up wasting more water than a standard toilet. The main issue is that removing and replacing an original equipment manufacturer’s (OEM) flush valve with an after-market product changes the full flush characteristics of the toilet fixture. The full removal of the contents of the bowl is dependent upon delivery of the right amount of water at the correct rate. Changing either of these factors can adversely affect flush performance, which may increase the need for double flushing, thereby increasing water use.

If dual-flush retrofit valves were performance tested with each model of the gravity-fed toilet into which they would be installed, this wouldn’t be an issue. But because such extensive testing would be expensive and largely impractical, it generally isn’t done for dual-flush kits

The Professor also notes that the half-volume flush is particularly vulnerable to providing an unsatisfactory flush because there may not be a complete exchange of water in the bowl. This makes it particularly likely that waste – and toilet paper especially – will remain in the bowl and require a second or even a third flush, completely negating any expected water savings.

The moral of the story: invest in a real, WaterSense-certified dual-flush toilet! They may cost more than a retrofit kit but they can produce real water savings, and will save you money in the long run.

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I agree. The kits do not work on some toilets, but they do on most. Isn’t it worth trying it on your toilet? All of the Kits I’ve seen, offer a full refund. If it doesn’t work, send it back. A lot of people don’t consider the environmental costs associated with junking your existing toilet in a already overflowing landfill. What about manufacturing a new toilet? How much energy does it take to fire the china used of a new toilet? A lot. How much water is consumed in creating that energy? A whole lot. Try a retrofit kit, unless you’d rather not try to save our planet.

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