What a Water Leak Really Costs You

A water leak costs anywhere from a few dollars a year to more than $1,000 a month, depending on how fast it runs and what your utility charges. A faucet dripping once per second wastes more than 3,000 gallons a year, roughly $30 at a combined water-and-sewer rate of $10 per 1,000 gallons. A toilet fill valve stuck open can waste 4,300 gallons a day, which the EPA puts at up to $1,400 a month. The cost of any leak is gallons lost multiplied by your rate, and you can measure both with your water meter and your latest bill.

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What common leaks cost at a glance

The EPA estimates that the average household loses more than 9,300 gallons a year to leaks, and that nine percent of homes leak 50 gallons or more per day. At our example rate, that average works out to roughly $93 a year. The table below pairs the EPA's published water-loss figures with a cost at $10 per 1,000 gallons.

Dollar figures are our estimates, calculated from the EPA gallon figures at the stated rate. The EPA's own cost examples (up to $1,400 a month for the stuck fill valve) run a little higher, which suggests a rate slightly above $10 per 1,000 gallons.

The pattern matters more than any single row. A drip is cheap, a fixture that runs continuously is expensive, and anything flowing at a gallon a minute costs thousands of dollars a year. Leak cost climbs with flow rate, and flow rate climbs quickly as a hole gets bigger.

Leak cost by flow rate

Most leaks are a steady trickle rather than a countable drip. If you can estimate the flow in gallons per minute, this table converts it to gallons and dollars. Leaks run around the clock, so even tiny rates add up over the 43,200 minutes in a 30-day month.

A trickle of 0.1 gallon per minute, about a cup and a half every minute, sounds trivial. It loses 4,320 gallons a month. The EPA's example of a drip-irrigation malfunction leaking one gallon per minute lands at $5,700 per year, which is the bottom row of this table carried out to twelve months.

How to calculate your own leak cost

Two steps turn a leak rate into a dollar figure. First convert the flow to gallons lost, then price those gallons at your rate.

Here is a worked example. Turn off every fixture, record the meter, and check again two hours later. Say it advanced by 5 gallons:

The water leak cost calculator does this arithmetic for any leak rate, duration and price, so you can compare a quick fix against living with the leak.

Why your rate changes the answer

The same leak costs different amounts in different towns, because utilities build bills from several pieces. Check yours for these:

• Water charge. Billed per 1,000 gallons or per CCF. This is the base price of every gallon that passes the meter.
• Sewer charge. Often tied to the water you use, so water that runs down a drain can be billed twice. Water that never reaches a drain, such as an irrigation leak, may not carry the sewer charge, depending on your utility.
• Tiered rates. Many utilities charge more per gallon as monthly use climbs. A leak can push you into a higher tier, so the extra gallons may cost more than your normal ones.
• Fixed charges. Base fees do not change with a leak, so leave them out of the calculation.

Add the water and sewer rates together for indoor leaks, then use that figure in the formula above. The rates in this guide are examples, not averages for your area.

Where the money actually goes

Four leaks account for most of the expensive household surprises:

Toilets. The expensive toilet leaks are the quiet ones. The EPA says a worn flapper can silently leak thousands of gallons a year and recommends replacing flappers at least every five years.

Irrigation and outdoor lines. Hole size matters more than most people expect. Flow scales with the area of the opening, and area scales with the square of the diameter. At the same pressure, we estimate a 1/16-inch hole would lose roughly four times the EPA's 6,300 gallons a month, about 25,000 gallons, and a 1/8-inch hole roughly 16 times as much, about 100,000 gallons. At a water-only rate of $6 per 1,000 gallons, that larger hole would cost around $600 a month.

Underground lines. A leak between the meter and your house never shows up as a drip. The signs are a meter that keeps moving with everything off, a soggy or unusually green patch of yard, or a bill that rises with no change in habits.

Costs that are not on the water bill

The metered water is the visible cost. Others can be larger:

• Property damage. A slow leak inside a wall, under a floor or behind an appliance can rot framing and flooring and encourage mold. Repairs often cost far more than the water that caused them.
• Energy. A leak on the hot side wastes the fuel or electricity used to heat that water as well as the water itself.
• Insurance. Many home insurance policies treat gradual, long-term leakage differently from sudden damage, so read your policy. The EPA notes that leak detectors and flow monitors can also reduce insurance premiums.
• Supply. The EPA estimates household leaks waste nearly 1 trillion gallons of water a year across the United States.

How to find a leak

These checks, drawn from EPA guidance, take under an hour and cost nothing:

1. Check a winter bill. Look at a cold month, when you use little outdoor water. A family of four above 12,000 gallons suggests a serious leak.
2. Run the meter test. Turn everything off, read the meter, and read it again after two hours. Any movement means water is running somewhere.
3. Dye-test every toilet. Add a few drops of food coloring to the tank. If color reaches the bowl within 10 minutes, the flapper leaks. Flush right away to avoid staining.
4. Inspect fixtures. Look for water around faucet gaskets, pipe fittings, showerheads and hose connections.
5. Check irrigation each spring. Frost can damage lines over winter.

Once you find a leak, the fix is usually cheap relative to the loss. The EPA says common household leaks such as worn flappers and dripping faucets are often easy to fix with a few tools and inexpensive parts, and that fixing them can save about 10 percent on a water bill. If you would rather not rely on periodic checks, a flow monitor on the main line can flag a leak anywhere downstream.

The bottom line

A leak costs gallons lost times your rate, and the number depends mostly on flow. A drip costs dollars a year, a steady trickle costs tens of dollars a month, and a stuck valve or a broken line can cost hundreds or more. Find your rate on your bill, run the two-hour meter test, and put the result through the formula. If the number is more than a few dollars a month, repair it now, before the water bill is the smaller part of the cost.