Low Water Usage Toilets

High Efficiency Toilets

High efficiency toilets, those that use 1.6 gallons or less per flush (1.6 gpf), have been marketed in the United States since the early 1980's. By 1992, seventeen States had established a standard of 1.6 gpf for replacement toilets and those installed in new construction. The Energy Policy Act of 1992 (EPAct) established a national manufacturing standard of 1.6 gpf for most toilets, the initial stage of which took effect on January 1, 1994.


Some anecdotal evidence of poor performance of 1.6 gpf toilets has been reported. The problems of clogging and inadequate bowl clearance necessitating multiple flushing have been recognized for both 1.6 gpf and higher flush volume toilets. Field and laboratory studies over the last thirteen years have shown very little overall difference in the incidence of clogging and multiple flushes between 1.6 gpf and 3.5 gpf toilets, although differences among individual makes and models have been noted. Some evidence also suggests that the plumbing problems of some consumers predate the EPAct standard and could be helped, worsened, or unaffected by the installation of a 1.6 gpf toilet.

Customer Acceptance

Surveys of thousands of 1.6 gpf toilet customers indicate that the great majority are satisfied with their toilet's performance. Some brands and models of high efficiency toilets received more positive responses than others. Some surveys concluded that the 1.6 gpf toilets which require the least frequent double-flushing tend to receive the highest purchaser satisfaction ratings. In a fairly recent (1996) survey in New York City, homeowners and plumbers gave positive average ratings to all but one of the 1.6 gpf toilet models installed. As market forces improve 1.6 gpf toilets over time, overall customer satisfaction should increase.

Water Savings

Toilets are the greatest water user in the house. Residential 1.6 gpf toilets have been shown to reduce toilet water use by 23% to 46% in studies conducted in a number of cities, including Tampa, Phoenix, Austin, and Oakland. A study published in 1999 by the American Water Works Association Research Foundation that looked in detail at the water use in nearly 100 homes in each of twelve North American cities concluded that high efficiency toilets save an average of 10.5 gallons per person daily.

Nationally, the use of high-efficiency toilets through new construction and normal replacements, is preliminarily estimated to save in excess of 7.6 billion gallons per day by 2020. This savings is nearly19% of the total amount of water supplied by U.S. public water systems in 1995.

Infrastructure Cost Savings

Use of high-efficiency toilets and other plumbing products due to EPAct will significantly reduce water demand and wastewater generation over time, which, in turn, can reduce or defer the capital investment needed for water supply and wastewater treatment infrastructure.

Accelerated installation of high-efficiency plumbing fixtures, especially 1.6 gpf toilets, through incentive programs has become a very cost-effective way for some municipalities to defer, reduce, or avoid capital costs of needed water supply and wastewater facilities. The magnitude of infrastructure savings achievable through incentive programs for toilet replacement is impressive. For example, New York City invested $393 million in a 1.6 gpf toilet rebate program that has reduced water demand and wastewater flow by 90.6 mgd, 7% of the city's total water consumption. The rebate program accomplished a net present value savings of $605 million from a twenty-year deferral of water supply and wastewater treatment expansion projects.

Santa Monica completed a 1.6 gpf toilet replacement program achieving permanent reductions in water usage and wastewater flows of over 1.9 mgd, representing a 15% reduction in average total water demand and a 20% reduction of average total wastewater flow. The cost of the rebate program was $5.4 million. The program will have a net savings of $6 million in the year 2002 due to avoided costs of water imports and wastewater treatment.

Other Benefits

High efficiency toilets are a key component of water efficiency programs conducted in cities across the country. These programs achieve a variety of environmental results in addition to reducing costs. Use of water efficient plumbing fixtures and appliances helps to maintain aquatic habitats; restore wetlands and fisheries; protect groundwater from depletion and contamination; and reduce the amount of energy used to pump, heat and treat drinking water and to pump and treat wastewater.


Despite the anecdotal reports of poor performance, customer surveys show that satisfaction with 1.6 gpf toilets is high. Analyses of toilet performance indicate that 1.6 gpf toilets require multiple flushes with about the same frequency as higher volume toilets. The plumbing industry has steadily made improvements in toilet technology and market forces should continue to improve overall performance with time.

The water savings from 1.6 gpf toilets is significant. The role of high efficiency toilets as a tool in reducing infrastructure costs is important in light of the 1997 estimate of national needs for drinking water and wastewater facilities totaling 280 billion dollars over 20 years. High efficiency plumbing products and appliances not only reduce water demand and wastewater flows but have other significant environmental benefits as well.

Last updated on Friday, June 28th, 2002
URL: http://www.epa.gov/owm/water-efficiency/toilets.htm

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