High water bill? How to find a hidden leak

A sudden high water bill often means water kept running somewhere you did not notice, often from a toilet, faucet, irrigation line, or buried service line. The fastest first check is simple: stop all water use and watch your meter or leak indicator. If it keeps moving, water is going somewhere, and you can narrow the problem down before the next bill gets worse.

Start with the bill, not the shovel

A high bill does not always mean a hidden leak.

Sometimes the reason is normal but easy to forget: summer lawn watering, filling a pool, guests staying over, or a change in routine. Start by comparing the bill to the same month last year, not just to last month. That helps you account for seasonal water use.

The EPA says that for homes with no outdoor water use in winter, a family of four likely has a serious leak if water use goes over 12,000 gallons, or 16 hundred cubic feet, in a month. That is a useful warning sign, especially if your habits did not change.

If your bill jumped and you cannot explain it, treat it like a leak until you prove otherwise.

If you are not sure where your meter is, or which part of the line may be yours, see The curb stop, meter and property line, explained and use the Water line responsibility check.

Do a meter test before you call anyone

Your water meter is the quickest way to confirm whether water is still flowing when everything should be off.

Philadelphia Water Department says that if the small leak-detection dial is moving when no one is using water, you have a leak somewhere. The EPA gives a similar test: read the meter, avoid all water use, then read it again 2 hours later. Austin Water gives a shorter version: check the reading again after 30 minutes.

That difference matters because local utilities do not all explain the test the same way. The basic idea is the same: no water use, then see if the meter changes.

Quick meter check

1. Turn off all water use inside and outside the home.
2. Make sure no dishwasher, washing machine, irrigation system, ice maker, or humidifier is running.
3. Find the meter and the leak indicator or small sweep hand.
4. Watch the dial for a moment. If it is moving, water is flowing.
5. Write down the meter reading.
6. Check again after 30 minutes or, if your utility recommends it, after 2 hours.
7. If the reading changed, you likely have a leak.

If your utility offers smart meter data, sign in and look for hourly or daily use. Austin Water says its customer portal can send custom notifications for sudden increases in water use that may point to a leak. Some utilities offer similar alerts.

Check the easy indoor leaks first

Most hidden leaks are not dramatic. They are quiet.

A toilet is the first place to check because it can leak without making much sound. The EPA recommends a simple dye test at least once a year: put a few drops of food coloring or a dye tablet in the tank and wait 10 minutes without flushing. If color shows up in the bowl, the toilet is leaking.

Many toilet leaks are caused by a worn flapper. The EPA says flappers should be replaced at least once every 5 years to keep a good seal and avoid leaks.

After the toilet, move through the home one spot at a time:

• Faucets and showerheads that drip or seep
• The base of toilets
• Under sinks
• Washing machine supply hoses
• Dishwasher connections
• Water heater area
• Utility sinks and basement fixtures

Do not forget rooms or fixtures that are used less often. Philadelphia Water Department specifically tells customers to check basement toilets and utility sinks, because these are easy to miss.

Also listen. A running sound behind a wall, in a crawl space, or near a utility area can be a clue even before you see water.

If you want a deeper overview of what to do when you think the problem may be beyond the fixture itself, see Water line leak in your yard: what to do.

Check outside if the inside looks dry

If the meter test suggests a leak but your indoor fixtures look normal, step outside.

Look at the obvious places first:

• Hose bibs and outdoor spigots
• Garden hoses left pressurized
• Irrigation or sprinkler zones
• Drip lines around plants
• Pool autofill lines

The EPA notes that damaged irrigation systems are a common source of water waste. Outside leaks can be harder to spot because the ground can absorb water before it ever reaches the surface.

Walk the route from the street toward the house. Watch for patches of greener grass, soft soil, standing water, or a strip of ground that stays damp when everything else is dry. Those signs can point to a buried service line leak.

That matters because the leak may not be in your indoor plumbing at all. It may be in the line that brings water from the main to the home.

If you need help figuring out where that line usually runs, or who may be responsible for it where you live, start with Who is responsible for the water line to your house? and then search your area with /find.

Service line responsibility is not the same everywhere

This is where many homeowners get tripped up.

The location of a leak does not automatically tell you who has to pay for it. Rules differ by city and utility.

For example, Austin Water shows a diagram stating that city responsibility ends on the customer side of the meter box. Philadelphia Water Department says customers are responsible for leaks from the connection to the water main and throughout the property. Those are not the same rule.

So if your high bill seems tied to a buried line, do not assume the utility will repair it, and do not assume it will not. Check first.

That is especially important near the curb stop and meter. These areas can sit close to the line between public and private responsibility, and local rules can be very specific about who may touch what.

If the leak appears to be outside, confirm the rule with the relevant official office before authorizing excavation or trying to operate any exterior shutoff.

You can also browse state-by-state pages if you want a starting point before calling.

When to call a plumber, utility, or leak-detection pro

If the meter keeps moving and you still cannot find the source, it is time to bring in help.

Call a licensed plumber when:

• The leak is likely inside the house
• A toilet, valve, or appliance connection seems to be the problem
• Water stains, damp drywall, or moldy smells suggest a hidden interior leak
• You need a repair record for your utility or insurer

Call the utility first when:

• You suspect the leak is at or near the meter box
• The problem may involve the service line before it reaches the house plumbing
• You need to confirm who is responsible
• You want to know whether permits, inspections, or a licensed contractor are required in your area

If you keep getting unexplained spikes, a leak-detection or flow-monitoring device may help. The EPA says these devices can detect unusual water-use patterns or moisture and, in some cases, can even trigger a shutoff valve to limit damage.

Ask about alerts, bill reviews, and assistance

Once you find the leak, do not stop at the repair.

Ask your utility whether it offers:

• Leak alerts through a smart meter portal
• A way to review daily or hourly water use
• A bill review after a verified leak
• Guidance on permits or inspections for buried line repairs
• Customer assistance or conservation programs

These programs vary a lot.

Austin Water says its smart meter system can provide near-real-time water use data and leak alerts through its customer portal. Philadelphia's TAP program says eligible customers can receive free water conservation services, and contractors can assist in fixing leaks for homes with high usage.

That does not mean your city offers the same help. Some places do, some do not, and the rules may differ by town, county, or utility district.

If the leak turns out to be on the service line, you may also want to read Water service line replacement costs and Water line warranty plans: worth it? before you decide how to pay for repairs.

Frequently asked questions

Can a toilet really cause a very high water bill?

Yes. Toilets are one of the most common hidden leaks because they can run quietly for days or weeks. The EPA recommends a dye test: add food coloring or a dye tablet to the tank, wait 10 minutes, and check whether color appears in the bowl without flushing.

What if my meter shows a leak, but nothing inside the house looks wet?

That often points to an outdoor problem, such as irrigation, a hose bib, or a buried service line leak. Check the yard and the route from the street to the house. If the leak may be on the service line, use /find or the Water line responsibility check to start sorting out who handles that section where you live.

Should I try to use the curb stop or open the meter box myself?

Only if your local utility says that is allowed and safe. Responsibility around the meter and curb stop varies by utility, and some systems treat those parts as utility equipment even when they sit near your property line.

Can I get help with leak repair costs or a high bill caused by a leak?

Maybe. Some utilities offer leak alerts, conservation visits, payment help, or repair assistance for eligible customers. Philadelphia's TAP program is one example, but programs and rules vary widely. Check with your utility billing office or water department and confirm any local requirements before you count on an adjustment or assistance.