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 December 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, and Texas 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 (similar to ENERGY STAR but focused on helping consumers identify water-efficient products).
According to EPA, toilets are one of the primary users of water in the home, accounting for 30% of an average home's indoor water usage. In the U.S., there are an average of 1.9 toilets per home.