Hi SamC Our unique designed valve calculates and controls the inflow water for 2L each flushing, We have tested over the past 5 years, it is among 1.8L-2.5L per flush, this kind of valve connects the water pipe directly, different from the traditional toilet need water storage, have a video to prove this test, the connection is http://www.zotran.hk/technology.asp? A_ID =20,If need more details or data, pls contact us by the mail or telephone, thanks. Here're the features: - Patent 2.0LPF flush system - Innovative mechanism design - Bold water conservation - 2.0L (0.53gal) per flush. - Quick discharge and refill – it takes 2~3 seconds only - Deodorization and no leakage - Low noise by built-in quieter in flushing mechanism Meantime, all Zotran UHET enjoys following warranty: - 10 years guarantee - Lifetime guarantee on porcelain - Lifetime maintenance for mechanism