The water service line — the pipe running underground from the meter to your house — is the one part of your plumbing you never see. When it leaks, the water drains straight into the soil, and the symptoms show up indirectly: in your yard, your bill, and your water pressure. Because these leaks are invisible by nature, homeowners often chase the wrong cause for weeks. Here is how to read the signs correctly.
How do I know if my underground water line is leaking?
Look for a cluster of these symptoms rather than any single one:
- Soggy or sunken spots in the yard — especially along the path from the meter to the house.
- One patch of grass growing faster and greener than the rest, even without extra watering.
- Low water pressure throughout the house, gradually getting worse.
- A water bill that keeps climbing with no change in usage.
- The sound of running water when everything is off — sometimes faintly audible near the meter or along the line's path.
- Cracks or settling in driveways, walkways, or patios above the line's route.
- Discolored water from taps, which can indicate a deteriorating line.
In Alhambra, many service lines are original to homes built decades ago — aging galvanized and copper lines are prime candidates for underground failure after years of soil movement and corrosion.
Rule out sprinklers first
This is the step most guides skip, and it prevents the most misdiagnosis. Irrigation systems leak too — stuck zone valves, cracked heads, and broken lateral lines create the exact same soggy spots and green patches as a service-line leak. Before suspecting the water line: run each irrigation zone and watch for geysers or pooling, then shut the irrigation off entirely at its own valve for a few days. If the wet spots dry up, the problem was irrigation. If they persist with the sprinklers off, the service line moves to the top of the suspect list.
Can a water meter detect an underground leak?
Yes — the meter test is the definitive do-it-yourself check. Turn off everything in the house and every irrigation zone, note the meter reading, wait one to two hours without using water, and read it again. Any movement means water is escaping on your side of the meter. To narrow it further, shut off the main house valve while leaving the meter-to-house line pressurized: if the meter still moves, the leak is in the underground service line between the meter and the house. That single test separates a service-line leak from every indoor suspect.
What does a leaking underground pipe sound like?
To the unaided ear, usually nothing — soil muffles the sound of escaping water, which is why these leaks stay hidden. But a ground microphone can pick up the hiss or whoosh of a pressurized leak through soil and pavement, and the loudest point sits roughly above the break. This is why acoustic listening is the primary professional tool for underground lines: it turns an invisible problem into a marked spot on the ground, so any digging is targeted instead of exploratory.
Will my yard always look wet if the water line leaks?
No — and this is why underground leaks go unnoticed for so long. A deep leak in sandy or well-draining soil may never surface; the water simply percolates downward, and the only symptoms are the bill and the pressure. Conversely, a shallow leak in dense clay soil shows up fast as a soggy patch. Do not wait for a swamp to appear before investigating — the meter test is far more reliable than your eyes.
What happens if an underground leak goes unfixed?
An underground leak does not fix itself — it gets worse. A small crack widens under constant pressure, the escaping water erodes soil around the pipe (which can cause settling under driveways and walkways), and the water bill keeps climbing every cycle. In the worst cases, prolonged saturation near the foundation can contribute to moisture problems inside the home. Because the leak is invisible, the damage compounds silently — which is why a positive meter test deserves prompt professional attention rather than a wait-and-see approach.
If the signs point to your service line, underground main line leak detection can pinpoint the break without tearing up the yard. Call +1 626-898-6221 — Alhambra Leak Pros is open 24 hours.
Related service: Underground Main Line Leak Detection in Alhambra, CA