Water leak calculator: what a drip or leak costs

How the calculator works

The USGS drip calculator assumes a faucet drip is about 1/4 milliliter, which works out to roughly 15,140 drips per gallon. USGS says measured sink drips ran from about 1/5 to 1/3 mL and bathtub drips about 1/2 mL, so the calculator offers both sizes.

• Gallons per day = drips per minute × 1,440 minutes × drip size in mL ÷ 3,785.41 mL per gallon.
• Cost = gallons × your rate. Rates billed per CCF (100 cubic feet) are converted at 748 gallons per CCF.
• A month is 30.4 days and a year is 365 days.

Use the combined water and sewer rate from your bill if your utility charges sewer by the gallon too. The $10 per 1,000 gallons filled in above is only a placeholder.

Worked example

A sink faucet dripping once a second is 60 drips a minute. That is 60 × 1,440 × 0.25 ÷ 3,785.41 = about 5.7 gallons a day, or about 2,080 gallons a year. At $10 per 1,000 gallons, that costs about $21 a year. EPA's Fix a Leak Week page puts the same one-drip-per-second leak at more than 3,000 gallons a year, which implies larger drips. Drip size is the biggest unknown, so treat the result as an estimate.

Toilet leaks are often bigger

A toilet leak can run silently all day, which is why the gallons-per-day mode is there. EPA WaterSense says a toilet that runs constantly can waste more than 200 gallons a day (EPA WaterSense Fix a Leak worksheet). To measure one, read your water meter, use no water for an hour or two, and read it again. EPA says nine percent of homes have leaks that waste 50 gallons or more per day.

If your toilet refills on its own, start with our guide on a toilet that runs every few minutes, which explains the dye test. If the bowl level drops instead, see why a toilet water level drops by itself.