The most common signs of a water main leak are water pooling near the street or driveway, soggy patches of lawn along the service line, a water bill that jumps with no change in use, lower water pressure throughout the property and the sound of running water when nothing is on. Because the main runs underground, these surface clues are often the only warning before damage becomes serious.
What is a water main?
The water main, or service line, is the pipe that connects a property to the public water supply. A larger utility main runs along the street, and a service line branches off it to each home or building. The line typically enters through the ground, a foundation wall or a utility closet and feeds the water meter and the rest of the plumbing. Every gallon you use passes through it, so a leak here can lose a great deal of water quickly.
8 signs of a water main leak
- Water pooling outdoors. Standing water in the street, gutter, driveway or parking area when it has not rained can mean a leak between the street and the building.
- Soggy or unusually green lawn. A persistently wet strip of lawn, especially along the path of the service line, points to water escaping underground.
- Damp or soft drywall. Where the line enters the building, a leak can wet nearby walls and leave drywall feeling soft or spongy.
- A higher water bill. A main leak runs constantly, so the bill rises well above the normal pattern for the season.
- Low water pressure. Pressure that drops at every fixture, rather than just one, can mean water is escaping before it reaches the house.
- Damage at the foundation. Ongoing water against or under a foundation can stain concrete and contribute to cracking over time.
- The sound of running water. Hearing water moving in walls, at the meter or near the line when every fixture is off.
- Musty odors or mold. Moisture behind walls or under floors near the entry point can lead to mold growth and a lingering damp smell.
A quick meter test
Turn off every faucet, appliance and irrigation zone, then watch the water meter. If the dial or leak indicator keeps moving, water is flowing somewhere. To narrow it down, close the main shutoff valve at the house: if the meter still moves, the leak is likely on the service line between the meter and the house. Our guide to reading your water meter walks through the process.
Signs that point somewhere else
Not every one of these signs means the main is leaking. A high bill can come from a running toilet or an irrigation leak, low pressure from a single clogged fixture or a pressure regulator, and wet lawn from a sprinkler line. Checking the obvious causes first, and then testing, avoids digging in the wrong place.
What to do next
If several of these signs line up, have the line checked before the leak undermines landscaping, hardscape or the foundation. Our article on what to do if you have a water main leak covers responsibility and next steps. Underground and service line leaks can usually be located without excavating to search, using pressure testing and acoustic equipment; see high water bill detection and mystery leak detection.
Call 1st Response Leak Detection at (619) 374-8554, 24 hours a day, or request service online.
