how much water is needed to flush the toilet?
Federal law currently mandates that all toilets manufactured in the United States use no more than 1.6 gallons per flush, but WaterSense-labeled models only require 1.28 gallons or less per flush. Toilets made from the early 1980s to 1992 typically used 3.5 gallons per flush (13.2 liters) or more.