October 2012
3-9
Water Use After Replacement
To estimate the water use of a WaterSense labeled replacement tank-type toilet, use
Equation 3-1, substituting the flush volume of the replacement tank-type toilet. Wa-
terSense labeled toilets use no more than 1.28 gpf on average.
Water Savings
To calculate the water savings that can be achieved from replacing an existing tank-
type toilet, identify the following information and use Equation 3-2:
••
Current water use as calculated using Equation 3-1.
••
Water use after replacement as calculated using Equation 3-1.
Equation 3-2. Water Savings FromToilet Replacement (gallons per year)
= Current Water Use of Toilet –Water Use of Toilet After Replacement
Where:
••
Current Water Use of Toilet (gallons per year)
••
Water Use of Toilet After Replacement (gallons per year)
Payback
To calculate the simple payback from the water savings associated with replacing an
existing tank-type toilet, consider the equipment and installation cost of the replace-
ment tank-type toilet, the water savings as calculated using Equation 3-2, and the
facility-specific cost of water and wastewater.
Flushometer-Valve Toilet Replacement
Current Water Use
To estimate the current water use of an existing flushometer-valve toilet, use Equa-
tion 3-1, substituting the flush volume of the existing flushometer-valve toilet. Toilets
installed starting in the mid-1970s typically have standard flush volumes of 3.5 gpf or
5.0
gpf.
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Toilets installed in 1994 or later have standard flush volumes of 1.6 gpf.
Water Use After Replacement
To estimate the water use of a replacement flushometer-valve toilet, use Equation
3-1,
substituting the flush volume of the replacement flushometer-valve toilet.
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North Carolina Department of Environment and Natural Resources, et al.,
op. cit.
3.2
Toilets
