What is a dual flush toilet? It’s a toilet that gives you the choice of a big flush or a small flush, depending on how much flushing power you need, and in regards to water volume. We probably don’t need to explain the circumstances that dictate one type of flush versus the other; needless to say it involves flushing either solid versus liquid. You choose which flush you want by using a separate button. This results in reductions in water consumption of 50 percent to 75 percent.