The amount of water used by a flush toilet is used as a measure of its efficiency.
Volume per Flush
3.5 to 5.0 gallons
low efficiency or high flow
single flush, 1.6 gallons
low flow or ultra low flow (ULF)
<= 1.28 gallons
high efficiency toilet (HET)
dual flush, < 1.0 gallons and <= 1.6 gallons
• A dual flush toilet has a low volume setting for urine and a higher volume for feces. The average water use per day is in the high-efficiency range.
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