How much does a leaky faucet cost?

Measure instead of guessing

Collect the drip volume for a timed interval, or count drops for a minute and repeat. A slow leak can vary with pressure and temperature, so take more than one sample.

Use the rates on your bill

Multiply daily gallons by the number of days in the billing period, then apply the water rate and any sewer charge that is based on volume. A hot-water leak can also carry an energy cost.

Repair the cause, not only the symptom

A worn washer or cartridge is common, but the correct part depends on the faucet. Shut off the local supply before disassembly, protect the drain, and call a plumber for a seized valve, concealed leak, or water near electrical equipment.

Useful signal: if the faucet is dry but the water meter moves with every fixture off, use the whole-home meter test instead of assuming the faucet is responsible.

A worked example

Collect the drip in a measuring cup for ten minutes and you have everything the calculation needs.

Say 2 fluid ounces collect in 10 minutes. That is 0.2 ounces a minute, or 288 ounces a day — 2.25 gallons, since a gallon is 128 fluid ounces. Over a 30-day billing period, about 67.5 gallons.

Many utilities bill by the thousand gallons or by CCF, one hundred cubic feet, which is about 748 gallons. At an illustrative combined water and sewer charge of $12 per thousand gallons, 67.5 gallons costs about 81 cents a month. A faster drip, a hot-water leak, or several leaking fixtures multiply that quickly.

Checking for leaks you cannot see

A dripping faucet is visible. A running toilet or a leak inside a wall often is not, and the water meter is how you find out.

Turn off every fixture and appliance that uses water, read the meter, and read it again an hour or two later without using any. If it has moved, water is going somewhere. The guide to finding a water leak walks through narrowing it down, and a running toilet is one of the most common silent leaks.