Toilets (also known as water closets) include tank-type toilets that are either gravity or pressure assist and either single- or dual-flush.
Congress established national toilet standards as part of the Energy Policy Act of 1992, and they took effect in 1994. Congress instructed DOE to update the standards when the American Society of Mechanical Engineers (ASME) amended their standards. In 2010, with no ASME revisions on the books, DOE officially waived federal preemption of the 1.6 gallon-per-flush (gpf) national toilet standard. This waiver of federal preemption allows states to set standards provided they are more stringent than the national standard.
California, Colorado, Georgia, Texas, Washington state, and New York City have adopted toilet efficiency standards that require products to use no more than 1.28 gpf. Products meeting the 1.28 gpf level currently meet the qualifications for the EPA WaterSense program (which is similar to ENERGY STAR but focused on helping consumers identify water-efficient products).
Toilets are one of the primary users of water in the home, accounting for 26% of an average home's indoor water usage, according to a 2016 Water Research Foundation study. In the U.S., there are an average of 1.9 toilets per home. ASAP estimates that 73% of all residential toilet models and 48% of all commercial toilet models meet the 1.28 gpf standard.