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Toilet Water Savings

Replacing your old toilet can save water – lots of water.

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 toilets that offer a 0.8 gallon flush for liquid and a 1.6 gallon flush for solids. The results are shown below in Table 1.

Table 1: Water use in homes with standard, 1.6 gallon, and dual flush toilets

Avg. Gallons per Flush
Avg. Gallons per Person Per Day
Non-conserving Home
Conserving home (1.6 gpf toilet)
Conserving home (dual flush toilet)

What happens when a family of four replaces all their toilets with new high efficiency models. Figure 1 shows a projection of the difference in water use for the standard non-conserving toilet, 1.6 gpf model, and dual flush model. The family would save more than 14,000 gallons of water per year by installing 1.6 gpf toilets and more than 17,000 gallons of water per year by installing dual flush toilets!

Figure 1: Annual toilet water usage with different fixtures.

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