Page 76 - WaterSense at Work

October 2012
For service sinks, install faucets that flow as low as possible without inhibiting
the use of the sink (i.e., if the sink’s function is volume-dependent, do not reduce
faucet flow rate to the point that it has to be used significantly longer).
Savings Potential
Water savings for both private- and public-use lavatory faucets can be achieved by
retrofitting existing faucets with aerators or replacing existing faucets. The same
amount of water savings can be expected for a retrofit or replacement, however,
retrofitting existing faucets with aerators will yield the shortest payback period due
to minimal equipment costs.
To estimate facility-specific water savings and payback, use the following information:
Current Water Use
To estimate the current water use of an existing faucet, identify the following infor-
mation and use Equation 3-5:
Flow rate of the existing faucet. Private- and public-use lavatory faucets installed
in 1996 or later have flow rates of 2.2 gpm or less. Some public-use lavatory
faucets installed in more recent years may flow at 0.5 gpm. Faucet flow rate is
typically inscribed directly on the fixture itself.
Average daily use time. The average private-use lavatory faucet use is approxi-
mately 8.1 minutes per person per day.
Public-use faucets can be used between
seconds and one minute per use, and used three or four times per occupant
per day.
Number of building occupants.
Days of facility operation per year.
Equation 3-5. Water Use of Faucet (gallons per year)
= Faucet Flow Rate x Daily Use Time x Number of Building Occupants x
Days of Facility Operation
Faucet Flow Rate (gallons per minute)
Daily Use Time (minutes per person per day)
Number of Building Occupants (persons)
Days of Facility Operation (days per year)
Mayer, Peter W., and DeOreo, William B. American Water Works Association (AWWA) and AWWA Research Foundation. 1998.
Residential End Uses of Water
Page 95.