upstream from the toilet fixtures to make sure that the conditions are appropriate for
effective waste transport.
For maximum water savings and performance, purchase the flushometer valve and
bowl in hydraulically matched combinations that are compatible in terms of their
designed flush volume.
Consider installing composting toilets in facilities where connecting to a plumbing
system is cost-prohibitive or unavailable.
Water savings can be achieved by replacing existing tank-type and flushometer-valve
toilets. To estimate facility-specific water savings and payback, use the following
Tank-Type Toilet Replacement
Current Water Use
To estimate the current water use of an existing tank-type toilet, identify the follow-
ing information and use Equation 3-1:
Flush volume of the existing tank-type toilet. Toilets installed starting in the mid-
s typically have standard flush volumes of 3.5 gpf or 5.0 gpf.
in 1994 or later have standard flush volumes of 1.6 gpf.
Average number of times the toilet is flushed per day, which will be dependent
on the facility’s male-to-female ratio. Female building occupants use the toilet
three times per day on average, while male building occupants use the toilet
once per day on average.
Days of facility operation per year.
Equation 3-1. Water Use of Toilet (gallons per year)
= Toilet Flush Volume x Number of Flushes x Days of Facility Operation
Toilet Flush Volume (gallons per flush)
Number of Flushes (flushes per day)
Days of Facility Operation (days per year)
North Carolina Department of Environment and Natural Resources, et al. May 2009.
Water Efficiency Manual for Commercial, Industrial and Institutional Facilities
Vickers, Amy. 2001.
Handbook of Water Use and Conservation