The most common types of high-efficiency toilets are single-flush, dual-flush and pressure assist. Some manufacturers that offer these toilets are Toto, Kohler, Gerber, Caroma and American Standard.
Most municipalities require single-flush high-efficiency toilets in new home construction. This type of toilet uses 1.6 gallons of water per flush. A dual-flush toilet offers two options: 1.6 gallons of water per flush for solids, and 0.8 to 0.9 gallons per flush for liquids. A pressure-assist system uses pressure from the water supply line to compress air inside a pressure tank. When the user flushes the toilet, compressed air propels the water into the bowl to forcibly push waste out. This type of toilet may use as little as one gallon of water per flush.