Signs of an underground water leak in your yard
One test answers this. Close the main valve where the water line enters the house, then watch the meter.
If the needle keeps moving or the digital flow rate stays above zero, water is escaping between the meter and that valve. Other signs that point the same way:
- Water standing in the meter box or the box staying muddy in dry weather.
- A damp, dark, or sunken strip in the gravel or soil, often in a straight line between the meter and the house.
- Weeds or one plant thriving in a part of the yard that gets no irrigation.
- A hiss at the front hose bib or at the pressure regulator when no water is being used.
- Pressure that has dropped across the whole house.
- Dampness coming through a driveway crack or along the edge of a walkway.
If the meter stops when the house valve is closed, the yard line is fine and the leak is inside or under the house. See slab leak detection.
What causes underground water line leaks
Service lines fail at joints and at stress points. Copper develops pinholes and wears where it touches rock. Galvanized steel, found on older properties, rusts through from the inside.
Glued PVC joints let go, and polyethylene splits where it was kinked or clamped. Tree and shrub roots pry at fittings as they grow. Vehicle weight on a shallow line under a driveway, a pressure regulator that has stopped doing its job, and old shovel damage from landscaping work are the other common causes.
How underground water leak detection works
- Confirm and measure. We repeat the meter test with the house valve closed and estimate how much water is being lost.
- Check what else is on the line. Irrigation, a pool autofill, or a hose bib in the yard is often tapped off the service line before it reaches the house. Each branch is shut off or tested so it doesn't get mistaken for a leak. A leak that turns out to be on the sprinkler side becomes an irrigation leak search.
- Trace the route. Service lines rarely run in the straight line people expect. A metal line is traced by putting a signal on it and following that signal with a receiver. A plastic line has no signal to follow, so the route is worked out from the meter, the entry point, and sound.
- Listen along the line. A ground microphone is placed at intervals along the route. The leak is where the noise peaks. Readings are compared on both sides to rule out a valve or fitting that's simply passing sound along.
- Use tracer gas if the leak is quiet. The line is isolated and filled with a hydrogen and nitrogen mix. The gas comes up through the soil above the leak and is picked up at the surface.
- Mark the spot and the line. We mark the leak and the path of the pipe near it, with an estimate of depth where the equipment gives one.
How Tucson soil hides an underground water leak
Tucson yards don't show leaks the way a lawn does. Much of the valley has caliche, a layer of soil cemented hard by calcium carbonate, at shallow depth.
Water leaking above caliche can't drain down through it, so it runs sideways along the pipe trench and can surface many feet from the break, or at the lowest point of the yard. Where the soil is sandy and loose, the opposite happens: the ground takes the water straight down and nothing shows at the surface at all.
Why this matters to you: the wet spot isn't a reliable place to dig. People regularly dig up a damp patch, find sound pipe, and keep trenching.
And because Tucson Water doesn't locate leaks on private property, everything from the meter to the house is the owner's to find and fix. Locating the leak before digging is usually cheaper than a second hole, especially when the first hole would be through a driveway.
What affects the cost of underground leak detection
- Pipe material. Copper and galvanized lines can be traced electronically and carry sound well. PVC and polyethylene take more time and often need tracer gas.
- Length of the run. A short city lot is a quicker search than a long driveway or a house set far back from the street.
- What is on top. Listening through open soil is the easy case. Concrete, pavers, thick rock, and landscape fabric each change how sound reaches the surface.
- Depth. Deeper lines are quieter at the surface.
- Background noise. A busy street, a pool pump, or wind makes acoustic work slower.
- Branches and unknowns. Old additions, abandoned lines, and forgotten tees have to be sorted out before the leak can be confirmed.
- Whether the house valve holds. If the main valve doesn't close fully, isolation takes extra steps.
When an underground water leak is an emergency
Shut the water off at the meter box and call if water is flowing toward the house, entering the garage, pooling against the foundation, or washing soil out from under a driveway, wall, or walkway. Do the same if the ground has sunk or opened up, or if the washout is near the gas meter or electrical service.
If you can't operate the valve in the meter box, call Tucson Water and ask them to shut the meter off. A steady leak that only shows on the meter can wait for a scheduled visit. You're paying for that water every hour, so get it located within days.
Water line repair or replacement after the leak is marked
We don't dig or repair. A plumber will usually excavate at the mark and replace the failed section. If the line is old galvanized steel, or if we find more than one leak, replacing the whole run from meter to house is often the better choice, and we'll say so when that's what the testing shows.
After the repair, close the house valve and check the meter again. It shouldn't move. Keep the repair receipt and a note of what was found.
Tucson Water offers bill adjustments for high use caused by leaks, and you'll want that paperwork when you ask. This is one part of our wider water leak detection in Tucson, and the same meter-first approach applies to every kind of leak we look for.
How to prepare for water line leak detection
- Locate the meter box and clear rock or plants off the lid.
- Find where the line enters the house and check that the valve there turns.
- Turn the irrigation timer off the night before so the ground isn't wet from watering.
- Tell us about past repairs, additions, or anything you know about where the line runs.
- Move vehicles off the driveway if the line may run beneath it.
Underground water leak questions Tucson homeowners ask
Who is responsible for a leak between the water meter and the house in Tucson?
The property owner. Tucson Water maintains the main and the meter. The service line past the meter, on your property, is yours, and Tucson Water doesn't locate leaks on private property.
Can you find a leak in a plastic water line?
Yes, but the method changes. Plastic pipe can't be traced with a standard locator signal and doesn't carry leak noise far.
The route is worked out from known points and listening, and tracer gas is often used to confirm the leak. Expect a plastic line to take longer than a copper one.
How close will the mark be to the actual leak?
On a metal line in open soil, the mark is usually close enough that a small excavation exposes the leak. On deep plastic lines or under thick concrete, the area may be wider. We tell you how confident we're so the plumber can plan the size of the hole.
There's no wet spot in my yard. Can I still have a service line leak?
Yes. Dry desert soil can absorb a leak for months without showing anything at the surface. If the meter moves with the house valve closed and no irrigation or pool fill is connected ahead of that valve, the line is leaking.
Should I repair the leak or replace the whole line?
One leak in a sound copper or plastic line is normally a spot repair. Several leaks, or a corroded galvanized line, point toward replacing the full run. We report how many leaks we found and the pipe material so you and your plumber can decide.
Do you need to turn my water off during the search?
Briefly, at different points, to isolate sections. For most of the acoustic work the line has to be under pressure. If tracer gas is used, the water is off for that part of the test and restored afterward.