EPA - Watersense

http://www.epa.gov/watersense/

WaterSense is a partnership program sponsored by EPA. It seeks to protect the future of our nation's water supply by promoting water efficiency and enhancing the market for water-efficient products, programs, and practices. 

Products bearing the WaterSense label are generally 20 percent more water-efficient than similar products in the marketplace. The WaterSense label will help you identify high-performance, water-efficient products and professional certification programs that embrace and encourage the use of water-efficient design. EPA issues specifications that set out the requirements that products and programs must meet to earn the WaterSense label.

Faucets: The maximum flow rate shall not exceed 1.5 gallons per minute (gpm)3

(5.7 liters per minute [L/min]) at a pressure of 60 pounds per square inch (psi) at the inlet, when water is flowing; and

The minimum flow rate shall not be less than 0.8 gpm (3.0 L/min) at a pressure of 20 psi at the inlet, when water is flowing.

Toilets: The maximum volume of water that may be discharged by the toilet, when field adjustment of the tank trim is set at its maximum water use setting, shall not exceed the following amounts:

For single flush fixtures: 1.68 gallons (6.4 liters) per flush

For dual flush fixtures: 1.40 gallons (5.3 liters) per flush in reduced flush mode and 2.00 gallons (7.6 liters) per flush in full flush mode.

The certification for shower heads has not been finalized as of May 10, 2008. However, the EPA estimates that these will be the parameters upon shower head certification:

Shower Heads: WaterSense anticipates establishing a single maximum flow rate somewhere between 1.5 gallons per minute (gpm) and 2.0 gpm (measured at 80 pounds per square inch (psi)of pressure). A maximum flow rate that falls within this range would represent between a 20 to 40 percent reduction from the current federally allowable maximum flow rate of 2.5 gpm established by the Energy Policy Act of 1992.

Showering is one of the top uses of residential water in the United States, representing approximately 17 percent of indoor water use-more than 1.2 trillion gallons of water each year.