New York Times, August 3, 2008
Fred A. Berstein
... Another device, also common in European hotels, raises similar issues. It saves a lot of water, but also forces guests to think about how they use resources. The device is a dual–flush toilet. Instead of one button to operate the toilet, there are two: one for a 0.8–gallon flush (for liquid waste) and one for 1.6 gallons (for solids). The toilets, which average just under one gallon per flush –– as opposed to 7 gallons for some older toilets –– are standard in much of the world. But in the United States, few hotels have installed them. ...
An American hotel that has tried the toilets, however, has reported no problems at all. ... Since the change, water use at the hotel dropped by about a million gallons a month, according to Eddie Wilcut, conservation manager of the San Antonio Water System. ...
November 8, 2007
Benjamin H. Grumbles, Assistant Administrator for Water, U.S. Environmental Protection Agency testified before the House, Subcommittee on Water Resources and Environment and the Committee on Transporation and Infrastructure. The testimony came as part of a report on the Region 8 headquarters in Greening, Colorado. The facility is an impressive example of green building technologies put to use.
"One of EPA’s newest and most impressive facilities, the Region 8 Headquarters, will save water through the use of high efficiency plumbing fixtures such as waterless urinals and Dual–Flush toilets."
Most Effective Home Improvement Project is a Dual-Flush
A recent study conducted in Seattle measured water use in single-family homes before and after installation of high efficiency toilets (Mayer, et. al. 2000). About half of the toilets installed were standard 1.6 gallon per flush (gpf) models. The other half were dual flush that offer a 0.8 gallon flush for liquid and a 1.6 gallon flush for solids.
Facts and statistics are from government and private studies. Depending on your household consumption habits, results may vary.