Flushology: How do Dual Flush Toilets Work?By
Press 1 for Number One, press 2 for Number Two. How much simpler can it get?
Dual flush toilets are a considerable advancement over that old 1970s wheeze: if it’s yellow, let it mellow. Today’s motto is go greener, but do it cleaner.
As noted here, on How Stuff Works, most dual flush toilets do not use siphonic action to clean the bowl. Until now, most dual flush toilets rely on what is known as a washdown flush. With a washdown flush, the push of water rushing from the tank to the bowl cleanses the bowl and removes waste. It is hopefully forceful enough to do a thorough job without as much of the pull that siphonic toilets create.
Push action that is forceful enough to cleanly remove waste is forceful enough to create splashing. Even the most enthusiastic dual flush owners will admit to keeping a brush and towel nearby for washdown models: the former to thoroughly clean the bowl, and the latter to dry off after unintended splashing.
The better bet is to look for new dual flush models that have perfected the true siphonic pull action of other toilets.