Water bill suddenly high: how to find a hidden leak

The meter doesn't lie: let it tell you.

The answer in 2 lines. Turn off every faucet and every appliance that uses water, write down or photograph the meter reading, and use no water for one to two hours. If the reading changed, or the small leak indicator on the meter dial spins, water is leaking after the meter. Check toilets first with a few drops of food coloring in the tank. Get the leak fixed quickly and keep the plumber's invoice or your receipts: many water utilities offer a one-time leak adjustment on the bill, but rules and deadlines are set locally.

The first 3 steps

Turn off all faucets and anything that uses water (washer, dishwasher, sprinklers, ice maker, water softener), but leave the main shut-off valve open.
Find your water meter (often in a box near the curb, in the basement or by the garage), photograph the reading with the time, and look for a small triangle or star-shaped leak indicator. Use no water for one to two hours, or overnight, then check again.
Keep the bill and any letter from your water utility: you may need them to ask for a leak adjustment.

Stop: danger

Wet wall, floor or ceiling near an outlet, light fixture or the electrical panel: don't touch anything wet. Turn off power at the breaker only if the panel is dry and you can reach it without stepping in water; otherwise leave the room and call your power company or 911.
Water heater: only look at the discharge pipe from the relief valve. Don't open or take apart anything on the unit: it is under pressure, may be powered, and the water can scald.
Meter box: lift the lid with a tool, not your fingers, and watch for insects and snakes in some regions. Water bubbling up in the street or the sidewalk: keep away and call your water utility.

Where the leak is hiding: what to check

Toilets: water trickling into the bowl, a tank that refills on its own, or a few drops of food coloring in the tank that show up in the bowl within 10 to 15 minutes without flushing. A worn flapper is the usual culprit and an easy fix (NYC DEP's toilet leak test).
Faucets and supply lines under sinks: drips, a damp cabinet floor. Usually a do-it-yourself job with the water off.
Water heater: water running from the relief valve discharge pipe, or pooling under the tank. Call a licensed plumber.
Irrigation, outdoor hose bibs, pool: soggy or greener patches of lawn, a hissing sound. A faucet is easy; a buried pipe is a job for a pro.
Service line or pipes in walls or under a slab: a spreading stain, a warm spot on the floor, the sound of running water with everything off. A plumber or leak detection company is needed.

To narrow it down, close the shut-off valves under each toilet: if the meter stops moving, the leak was in a toilet. City guides such as Chandler, Arizona's and Santa Clara, California's show how to read the meter step by step.

What you can do yourself, and where to stop

The dye test in every toilet, and the meter test valve by valve.
Small visible leaks: a toilet flapper or fill valve, a faucet washer or cartridge, a supply hose. Take the old part to the hardware store to buy the same size.
Read the meter weekly for a month after the repair to check that use goes back down.
Stop there: buried service lines, pipes in walls or under a slab, the water heater, or a meter that keeps moving when you can't find anything. Call a licensed plumber. Leaks on the utility's side of the meter (or at the meter itself) are for the water utility to fix.

If the meter doesn't move

No leak right now? Compare the bill with the same period last year: a new household member, a filled pool, summer watering or a leak already fixed can explain it. Check whether the bill was based on an estimated reading rather than an actual one, and compare the reading on the bill with what your meter shows. If something still doesn't add up, ask the utility to re-read or test the meter; some charge for the test if the meter turns out to be accurate.

What not to do

Opening a wall or breaking up a slab to look for the leak yourself: a plumber can often locate it first with listening or pressure tests, and your insurer may need to see the damage.
Paying a huge bill without asking about a leak adjustment, or missing the utility's deadline to ask.
Ignoring a toilet that runs "just a little": it can waste a lot of water over a billing period.

Who pays, and who to tell

Leak adjustments: there is no nationwide rule. Many cities and water districts will credit part of the extra water (and sometimes sewer charges) once, if you repair the leak quickly and send proof such as a plumber's invoice or parts receipts, within a deadline. Look for "leak adjustment" on your utility's website or call the number on your bill. Examples: Hillsborough County, Florida and Asheville, North Carolina.
Renters: tell your landlord in writing right away. Plumbing repairs are usually the landlord's job; who pays the water bill depends on your lease and local law.
Water damage from the leak: homeowners and renters policies usually cover sudden, accidental damage, not the cost of the wasted water and often not damage from a slow leak that went on for months (NAIC). Check your policy.

The figures (latest published)

EPA WaterSense estimates that household leaks can waste nearly 10,000 gallons a year in an average home, that about 10% of homes have leaks wasting 90 gallons or more a day, and that leaks waste nearly 1 trillion gallons nationwide each year (EPA WaterSense, Fix a Leak Week; Fix a Leak Week 2026 ran March 16 to 22, 2026). These are long-standing EPA estimates, not a new 2026 measurement.

Good to know

Read your meter on the same day every month: an unexplained jump is the first warning sign.
Do the toilet dye test twice a year.
Many utilities now have online portals or smart meters that can alert you to continuous use: check whether yours offers leak alerts.
Find your main shut-off valve before you need it: see our guide on shutting off the water.

In Phoenix, Daniel's water bill is more than double the usual amount. That evening he turns everything off and photographs the meter; in the morning the reading has moved. The food coloring stays in the toilet tanks, so it isn't a toilet. A plumber finds a cracked irrigation line under the lawn. Daniel sends the invoice to the city's utility with a leak adjustment request and gets part of the extra water credited.

A made-up story, for illustration.

Bobby

Sources, verification, confidence

Verified on November 1, 2026, for the United States. Confidence: high for the meter and dye tests and the safety steps; medium for leak adjustments, which vary from one utility to the next. This guide describes common cases, not a diagnosis.