The signs
- A warm or hot patch on a tile or concrete floor
- The sound of running water with every tap off
- A water bill that jumps with no change in use
- Damp carpet, lifting wood floor or new cracks in tile
- Hot water running out sooner, or the water heater running constantly
The first hour
- Do the meter test
Turn off every tap and appliance that uses water, then watch the leak indicator on the meter for a few minutes. If it moves, water is leaving the system.
- Close the house valve
If the meter stops when the house shut-off is closed, the leak is inside the house or under it, not in the yard line. Where to find the valve.
- Hot line? Turn off the heater
A warm floor means the leak is on the hot side. Turn off the water heater and close its cold inlet valve, which stops that leak while the rest of the house keeps water.
- Take photos and keep the bill
Pictures of the wet or warm area and the high bill help with both insurance and a SAWS leak adjustment.
What not to do
Do not let anyone start breaking concrete on a guess. A leak under the slab can travel along the pipe and surface feet away from the break, and the warm spot is not always directly over it. Insist that the leak is pinpointed with leak detection first. And do not leave it for weeks: water running under the foundation keeps washing out the soil it sits on, and in our expansive clay that can add foundation movement to the plumbing bill.
The repair options
- Spot repair: open the floor at the leak, repair the pipe, close it up. Best for a single leak in otherwise sound pipe.
- Reroute: abandon the leaking line under the slab and run a new one through the attic or walls. No concrete broken, and future leaks on that line are reachable.
- Repipe: when the house has leaked more than once, replacing the supply pipework is often cheaper than the third spot repair. See repiping.
Typical San Antonio prices for detection and each kind of repair are on our cost guide.
Why slab leaks are so common here
Much of Bexar County and the land toward the Hill Country sits on clay that swells in wet weather and shrinks in drought. Copper lines cast into the slab flex with that movement until a pinhole opens, and hard water wears the inside of the pipe at the same time. In rockier areas like Helotes the soil moves less but digging is slower, which makes locating the leak precisely even more important.
Questions people ask
Is a slab leak an emergency?
It is urgent. Water running under the foundation wastes water around the clock and can undermine the slab. If water is coming up through the floor, shut off the main and call straight away.
Will homeowners insurance cover it?
Policies vary. Many cover the cost of getting to the leak and the resulting water damage, but not the pipe repair itself. Call your insurer early and keep the plumber’s written findings.
Can I still use water while I wait?
If the leak is on the hot line, turning off the water heater and its cold inlet usually lets you use cold water normally. If it is on the cold side, keep the main closed except when you need it.
How is a slab leak found without digging?
The line is pressure tested to confirm the leak, then acoustic listening, line locating and thermal imaging narrow it to a small spot before anything is opened.