The water service line — the pipe running underground from the street meter to your house — is one of the most leak-prone parts of a home's plumbing and one of the least visible. In most cities, including Hawthorne, everything on your side of the meter is the property owner's responsibility. With the city's median home built around 1970, many of these buried lines are original galvanized steel or early copper — materials that corrode, pit, and eventually pinhole after half a century underground. Because the pipe is buried, its leaks announce themselves indirectly: in the yard, in the bill, and in the water pressure. Here's how to read those signs.
Why is one patch of my yard greener or soggy while the rest is dry?
This is the classic signature. A leaking service line constantly waters the soil above it, so one strip or patch of lawn grows faster, greener, and lusher than everything around it — even in dry weather. You may also find soil that stays soft or soggy days after watering, a low spot that never fully dries, or (on paved areas) a section of walkway that's perpetually damp. The leak is effectively irrigating that one area 24/7. If the green patch sits roughly along the line between your water meter and where the pipe enters the house, suspicion should be high.
Does whole-house low water pressure point to the main line?
It can. A leak in the service line bleeds off pressure before water ever reaches your fixtures, so pressure drops everywhere at once — showers, faucets, hose bibs. The key distinction: if only one fixture is weak, the problem is local (aerator, valve, that branch). If the whole house has gradually lost pressure and the neighbors haven't, the service line is a prime suspect. A sudden pressure drop paired with a soggy yard is about as clear as underground symptoms get.
How do I rule out my sprinkler system before suspecting the main?
Do this first — it's the most common false alarm. Turn the irrigation controller completely off for 48 hours. If the soggy area dries out, the sprinklers were the cause (check for a stuck valve or broken head). If it stays wet with the system off, the water is coming from somewhere else. Also walk the sprinkler zones while running: geysers, misting heads, and valve boxes full of standing water are sprinkler problems, not main-line problems. Only after irrigation is cleared should you escalate to the service line.
What does a hissing sound near the water line mean?
On a quiet day, put your ear near the water meter box (carefully — lift the lid, don't climb in) or along the suspected pipe path. A faint, steady hiss or whoosh with all household water off is the sound of pressurized water escaping underground — the same sound acoustic detection equipment amplifies and traces. Note where it seems loudest; that detail helps a technician enormously. No sound doesn't rule out a leak (small leaks can be nearly silent), but a clear hiss is strong confirmation.
The meter test that proves it
Here's the decisive home test: turn off the house's main shutoff valve (usually where the line enters the house, in the garage, or at the meter box), then watch the water meter for 30–60 minutes. If the meter still moves with the house fully isolated, water is escaping between the meter and your shutoff valve — that's the underground service line, confirmed. If the meter stops, the leak is inside the house instead. Either way, you've just saved the technician's first half-hour and pointed them in the right direction. Jot down the start and end readings with timestamps — a pro will want those numbers.
What to do next
Underground leaks don't fix themselves — they erode soil, waste thousands of gallons, and can undermine walkways, driveways, or foundations over time. Left long enough, a service-line leak can even wash out enough soil to create a visible sinkhole in the yard. If your tests point to the service line, underground water main leak detection uses acoustic listening and line tracing to mark the exact spot, so any repair digs one hole, not a trench. Call Hawthorne Leak Finders at +1 424-544-0197 — open 24 hours.
Related service: Underground Water Main Leak Detection in Alhambra, CA