How Dual Flush Toilets Work

The Future of the American Flush: High Efficiency Toilets

In 1994, the National Energy Policy Act was signed into law. It requires that toilets sold in the United States use no more than 1.6 gallons (6 liters) per flush [source: Green Living]. This mandate to conserve has given rise to a new generation of high efficiency toilets (HETs) that use technologies like pressure-assist, gravity flush and dual flush to whisk away waste using as little water as possible. Of the new technologies, the dual flush method has the advantage of intuitive flushing, where the operator can decide electively that less water is needed and use one gallon (3 liters) or less per flush instead of the 1.6 gallon maximum.

Although toilets purchased for new construction and retrofits must meet the new standards, millions of older water-guzzling toilets are still out there. As water and sewer costs keep rising, low flow toilets are becoming more attractive to the American consumer, and local and state governments are using rebates and tax incentives to encourage households to convert to these new technologies.

The advantages of low flow toilets in conserving water and reducing the demand on local water treatment facilities is pretty obvious. According to USA Today, the average person flushes the toilet five to eight times a day, and at a greedy five gallons a flush, the numbers start to add up quickly [source: Winter]. According to the Environmental Protection Agency, completely eliminating old style, water guzzling toilets would save about 2 billion gallons of water each day in the United States [source: Green Living]. With a growing population, an aging water treatment infrastructure and the looming threat of global warming contributing to uncertain weather, water conservation will continue to be a big issue.

How does the dual flush toilet fit into this picture? No one knows for sure. Most major toilet manufacturers are gearing up to provide these water saving toilets, but whether or not the American public will embrace a change in the way they approach their bathroom habits remains to be seen.

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  • All About Toilets. "A Guide to ­How Toilets Work." Undated. 10/10/08.
  • Biotechnology Innovations, Australia. "Dual Flush Technology." Undated. 10/2/08.
  • California Urban Water Conservation Council. "This issue…all about DUAL-FLUSH toilet fixtures." 2003.10/2/08.http.://
  • Canada Mortgage and Housing Corporation. "Dual-Flush Toilet Project." 4/2002, 10/2/08.
  • Casebier, Brad. "Dual Flush Toilet." Radiant Plumbing. 7/2008. 10/2/08.
  • City of Austin. "Choosing a Toilet." Undated. 10/2/08.
  • Consumer Reports. "Toilets Comfortable and Efficient." 1/2008. 10/2/08.
  • Consumer Search. "Toilets." 5/06. 10/2/08.
  • Dual Flush Toilets. "Dual Flush Toilets." Undated. 10/2/08.
  • Economically Sound. "Product Review - Ultra-Low Flush Toilets." 10/2004. 10/2/08.
  • Environmental Home Center. "Dual-Flush Toilets." Undated. 10/2/08.
  • "High Efficiency Toilets." Undated. 10/9/08.
  • "Tank Type High Efficiency Toilet Specs.1/2007.10/9/08.
  • "Watersense Labeled Toilets." Undated. 10/9/08.
  • Green and Save. "Dual Flush Toilets." Undated. 10/2/08.
  • Green Building Supply. "Dual Flush" Water Saving Toilets Never Clog." Undated. 10/5/08.
  • Green Building Supply. "Who is Caroma." Undated. 10/5/08.
  • Green Living. Love to Know. "Dual Flush Toilet." Undated. 10/2/08.
  • Innovations. "From Outside the Privy to Toilet Suite." Undated. 10/02/0.
  • Jones, Alan J. " Innovation: from outside privy totoilet suite." Undated. 10/5/08
  • Lowes. "Replacing a Toilet." Undated. 10/10/08.
  • MSN Money. "American Water Joins EPA's WaterSense Program." 9/19/2008.10/2/08.
  • Nash, Jenny. "The Lowdown on Low-Flow Toilets". HGTV Bath Design. Undated. 10/05/08.
  • Our Only Home. "Install a Dual Flush Toilet." 9/13/2008.10/5/2008.
  • Petz. " "Dual Flush Toilet - How to Retrofit and Upgrade Your Old Toilet." 5/13/08. 10/5/08.
  • Plumber and Mechanical. " Thomas Crapper: Myth & Reality."6/93.10/5/08.
  • Ramano, Jay. "Your Home - Reducing Water Use in the Home." The New York Times. 4/14/02.10/5/08.
  • Service Magic Home Improvement. "Dual Flush Toilets." Undated. 10/2/08.
  • Safe Plumbing - Plumbing Manufacturers Institute. "Water Efficiency." Undated. 11/05/2008.
  • Southern Nevada Water Authority. "Toilet Tips." Undated. 10/9/08.
  • The International Center for Bathroom Etiquette. "Germany." Undated. 10/10/08.
  • U.S Environmental Protection Agency. "Test Your Water Sense." Undated. 11/4/2008.
  • Winter, Michael. "No Joke - It's World Toilet Day. USA Today, 11/19/07. 10/10/08.