2.4b Dual-flush Toilets

Feature	Also known as high-efficiency toilets, these fixtures have two buttons: one to flush liquid waste and one to flush solid waste.  The full flush uses about 1.6 gallons of water, while the half flush uses about half of that.
Function	According to the NAHB Research Center: Designed for water conservation, high-efficiency toilets (HETs) have been defined by the plumbing industry and the EPA as those that use an average of 20 percent less water per flush than the industry standard of 1.6 gallons (or, 1.28 gallons). Using a high-efficiency unit (in place of 1.6-gallon flush units) can save up to 8,760 gallons of water each year for a family of four with average daily flushes of six each. In municipalities like Washington, D.C. this roughly translates to a water/sewer usage annual savings of $50. Savings will be greater in climates were water is in shorter supply.
Cost Range	Standard toilets range in cost from $100 to well over $1,000. HETs (high-efficiency toilets) are available in the same range. Water authorities in climates where water is scarce, like some western states, may offer rebates for installing HETs.
Brands	High-efficiency toilets with EPA’s WaterSense label include: American Standard, Briggs, Caroma, CEU, Crane, Duravit, Foremost, Gerber, Glacier Bay (a Home Depot brand), Greentide, Hennessy & Hinchcliffe, Kohler, Mansfield, Medyag, Niagara, OPS, Pegasus (Home Depot), ProFlo, Seasons, Sterling, Toto, VitrA, Vortens, and Zum. See the whole list
Cost savings	According to the EPA’s WaterSense: A family of four that replaces its home's older toilets with WaterSense labeled models will, based on a national average, save more than $90 per year in reduced water utility bills, and $2,000 over the lifetime of the toilets. Fact sheet