GB_Proficiency(300)Water Matrix. The WaterSense-certified Proficiency ultra-high-efficiency toilet uses just 0.8 gallon per flush to effectively evacuate both solid and liquid waste, consuming 37% less water than standard high-efficiency toilets. Its patented vacuum-assist flush technology produces a swift, powerful, and quiet flush, according to the maker. The unit features a stylish design with concealed trapway and easy cleaning surfaces.