How to Find and Fix an Outdoor or Underground Water Leak

A leak in your buried water line behaves differently from one inside the house. There is no dripping sound under a cabinet and no stain spreading across a ceiling. Instead the evidence shows up outdoors and on paper: a patch of lawn that stays soggy or unusually green during a dry stretch, a water bill that climbs for no reason you can name, or pressure that sags at every fixture. The water is escaping underground, somewhere between the street and your house, and the first job is not to dig. It is to confirm the leak is really outside, figure out which buried line is losing water, and measure how much. You can do all of that yourself. The actual repair of a buried supply line is a different matter, and this guide is clear about where your part ends.

The Signs a Leak Is Outdoors and Underground, Not Inside

An underground supply leak announces itself through the yard and the meter rather than through visible drips indoors. The most reliable tells are a wet or muddy spot that never dries out, grass or weeds that grow faster and greener over one strip of the lawn, the sound of water running when every fixture in the house is off, and a water bill that jumps without any change in how you use water.

The reason these symptoms point outdoors is plumbing layout. The line that carries pressurized water from the street to your home runs underground, and so do the lines feeding most irrigation systems. When one of them cracks or loosens at a fitting, the water has nowhere to go but into the surrounding soil. Unlike an interior leak, it rarely reaches a surface you can see, so it can run for weeks before the lawn or the bill gives it away.

Before you assume the problem is buried, rule out the easy indoor culprits. A running toilet, a dripping faucet, or a soft spot near an interior wall is a different investigation. For finding leaks inside the home, see our guide on signs you have a hidden water leak (108) and our guide on how to find the source of a water leak (109). A leaking outdoor faucet at the spigot itself is its own fix and is covered in our guide on why your outdoor faucet leaks or won’t shut off (161). This post assumes you have already checked those and the trail leads underground.

Is It the Irrigation System or the Main Service Line? How to Tell Them Apart

You can split this problem in half before anyone touches a shovel by isolating the irrigation system and watching the meter. If shutting off the irrigation makes the meter stop, the leak is in the sprinkler lines. If the meter keeps moving, the leak is on the main service line feeding the house.

Here is the method. Find the irrigation system’s dedicated shutoff valve, often near where the supply branches off for the sprinklers or at the backflow preventer, and close it. With irrigation isolated and no water running inside, watch the meter for movement (the next section explains exactly how to read it). A meter that goes still means the loss was downstream of that valve, in the irrigation piping. A meter that keeps creeping means water is still escaping from the service line itself, upstream of the irrigation branch.

This single test changes who you call and what gets dug. An irrigation leak lives in shallow, low-pressure poly tubing and is often a homeowner-friendly repair or a job for an irrigation specialist. A service-line leak is in the pressurized pipe that supplies your whole home, usually buried deeper, and it is a more serious dig. To understand the backflow device that protects your drinking water from the irrigation side, see our guide on what an irrigation backflow preventer does and why it’s required (164). Do not skip the isolation step. Guessing wrong here is the difference between repairing a sprinkler fitting and excavating your front yard.

Using the Water Meter to Confirm and Size the Loss

Your water meter is the one tool that both confirms a hidden leak and roughly measures it. The EPA’s WaterSense program describes the core check plainly: note the meter reading, avoid using any water for two hours, then read it again, and if the number has changed at all you probably have a leak.

Start by finding the meter, usually in a covered box near the curb or, in colder climates, in the basement. Many meters have a small flow indicator, often a tiny triangle, star, or sweeping hand, that spins whenever water moves through. With every fixture, appliance, and the irrigation off, watch that indicator. If it turns at all, water is flowing somewhere it should not be. For a longer confirmation, record the full reading, leave the water untouched for two hours, and compare. According to the EPA, household leaks can waste nearly 1 trillion gallons of water nationwide each year, and the average home’s leaks account for more than 9,300 gallons annually, so even a slow underground loss adds up fast on your bill.

To size the loss, take two readings a known number of hours apart with no water used, then look at how many gallons or cubic feet the dial moved. That gives you a leak rate you can hand to a plumber, which helps them judge urgency. For outdoor systems specifically, the EPA notes that an irrigation leak just 1/32 of an inch across, about the thickness of a dime, can waste roughly 6,300 gallons a month. This post summarizes the meter check; for the full step-by-step on reading the dials and unit math, see our guide on how to read your water meter to check for leaks (110).

Narrowing the Wet Spot Without Digging Up the Yard

You can usually narrow where a buried leak sits using surface clues and the meter, without excavating anything. The goal is to hand a professional a target, not a whole lawn.

Walk the likely path of the service line, which generally runs in a fairly straight route from the meter or curb stop toward where the line enters the house. Look for the surface tells: the softest, wettest ground, the greenest or fastest-growing grass, a spot that stays muddy after everything else dries, or low areas where escaping water pools. Pressing a long screwdriver or a stiff rod into the soil along that path can help you feel for unusually saturated ground, though this only works in soft earth and tells you nothing about depth. On a quiet night with traffic and appliances off, you can sometimes hear the faint hiss of water escaping a pressurized line near the leak.

Resist the urge to start digging based on a hunch. A wet surface spot can sit several feet to one side of the actual break, because pressurized water travels through soil and surfaces wherever it finds the path of least resistance. Professionals localize buried leaks with acoustic listening equipment and correlators that pinpoint the break far more precisely than surface signs alone. Your narrowing work is valuable because it shortens their search and your bill, but it is preparation for a repair, not the repair itself.

Why Repairing a Buried Service Line Is Excavation Work for a Licensed Plumber

Repairing a buried main or service line is excavation work, and it belongs to a licensed plumber, not a weekend project. Finding and confirming the leak is the do-it-yourself scope here. Opening the ground to fix it is not.

The reasons are practical and safety-driven. The service line is pressurized, often buried below the frost line, and may run under a driveway, walkway, sidewalk, or landscaping. Exposing it means digging a trench deep enough to work in safely, and an unsupported trench can collapse. The buried pipe sits alongside other utilities, so before any shovel goes in the ground, you are legally and practically required to have those lines located. In the United States, call 811, the free national “before you dig” service, a few business days ahead of any digging. A locator marks the approximate position of buried gas, electric, water, sewer, and communication lines with paint or flags so the dig does not strike them. Hitting a buried gas or electric line can cause serious injury, so this step is not optional.

For these reasons, treat a confirmed service-line leak as professional territory. A licensed plumber has the locating, excavation, and pipe-repair tools to open the ground, fix or replace the damaged section, and backfill correctly, and they will coordinate the 811 locate as part of the job. If you are facing a sudden break rather than a slow underground seep, see our guide on what to do when you find a burst or leaking pipe (114) for the immediate steps.

Who Owns the Pipe: Where Your Responsibility Ends and the Utility’s Begins

The buried service line is not always entirely yours, and knowing the ownership boundary tells you who pays and who you call. In many systems the demarcation point is the water meter or the curb stop near the property line: the utility owns the line and the meter up to that point, and the homeowner owns the service line from there to the house. Where exactly that line falls varies from one water provider to another, so the only authoritative answer comes from your local water utility.

This boundary matters before you spend a dollar on repairs. If the leak is on the utility’s side of the meter or curb stop, the water provider typically handles it. If it is on your side, the buried run between the meter and your house, the repair and its cost fall to you. Some utilities also offer or sell service-line protection plans, and the specifics differ everywhere. The practical move is one phone call: ask your water provider where their responsibility ends, whether your leak’s location sits on their side or yours, and what they cover. That answer reshapes the whole repair before any digging starts.

Frequently Asked Questions

How do I know if my underground water leak is irrigation or the main line?
Close the irrigation system’s shutoff valve and watch the water meter with no water running indoors. If the meter stops, the leak is in the irrigation piping downstream of that valve. If the meter keeps moving, the leak is on the main service line feeding the house. This isolation test splits the problem before anyone digs.

Who is responsible for a leak in the buried water line to my house?
It depends on where the leak falls relative to the ownership boundary, which is often the water meter or curb stop near the property line. The utility typically owns the line up to that point, and the homeowner owns the run from there to the house. The exact boundary varies by water provider, so confirm it with your local water utility before arranging repairs.

Can I dig up and fix the buried leak myself?
Finding and confirming the leak is a reasonable do-it-yourself task. Fixing a buried service line is excavation work that involves a pressurized line, possible trench collapse, and other utilities nearby, so it is a job for a licensed plumber. Before any digging happens, the buried utilities must be located through the free 811 service.

Why is my water bill high but I see no water inside?
A pressurized underground supply or irrigation leak loses water into the soil rather than onto a visible surface, so it can run for weeks while only the bill and a damp patch of yard show it. Use the two-hour meter test described above to confirm a hidden leak.

This article is general information, not professional advice. Underground leak repair and any excavation involve safety risks and local rules; consult a licensed plumber and your local water utility for your specific situation.

Sources

• EPA WaterSense, Fix a Leak Week (water meter check, household leak figures, irrigation leak figure): https://www.epa.gov/watersense/fix-leak-week
• EPA WaterSense (home page and leak detection program): https://www.epa.gov/watersense
• 811 Before You Dig (national call-before-you-dig service): https://811beforeyoudig.com/