Signs of a slab leak, and how one gets fixed
A slab leak is a broken water line under your home’s concrete foundation, either a supply line or sometimes a drain line. It doesn’t always show up as a puddle. You’ll usually notice a warm spot on the floor, a jump in your water bill, or the sound of water running when every faucet in the house is off.
Signs worth paying attention to
- A warm or hot patch on the floor, usually over a leaking hot water line
- The sound of running water somewhere in the house with every fixture off
- A water meter that keeps moving even when nothing’s using water
- Flooring that’s damp, buckling, or lifting for no obvious reason
- A musty smell that won’t go away, especially near one part of the floor
- Cracks in the floor or in nearby walls that weren’t there before
- A water heater that seems to run nonstop, working to keep up with a hot line that’s losing water underground
- A water bill that’s climbed with no real change in how you’re using water
One sign by itself proves little. A few of them together, especially the warm spot plus a bill that’s jumped, point pretty hard at a slab leak.
Confirm it before you tear anything up
Before you assume the worst, do the meter test. Shut off every fixture and appliance in the house, then watch the small leak indicator on your meter face. If it’s spinning with nothing running, water is going somewhere it shouldn’t. We walk through the full test in our post on a high water bill and a hidden leak. It won’t tell you where the leak is, just that one exists.
How a plumber finds the exact spot
Plumbers find slab leaks mostly by listening. Acoustic equipment picks up the sound of water escaping under pressure, and the plumber moves it around the floor until the sound peaks over one spot. For a leak on the hot side, thermal imaging can pick up a warm line running under the slab, which narrows things down fast. On a trickier job, a plumber may pressure test sections of pipe one at a time to isolate which line is losing pressure.
The goal is to break the floor once, in the right place.
What fixing one involves
There are three common paths, and which one makes sense depends on the leak.
- Spot repair. The floor gets opened at one specific point, the bad section of pipe gets cut out and replaced, and the concrete goes back. This works well when there’s one leak in an accessible spot and the rest of the pipe is in decent shape.
- Reroute the line. Instead of going back into the slab, the new pipe runs through the attic or walls and bypasses the damaged section. This skips cutting concrete, which matters if the leak sits under something like a load-bearing wall or a finished floor you’d rather not touch.
- Repipe. If the pipe is old enough, or leaking in more than one spot, patching one section just buys time before the next one lets go. A full repipe replaces the supply lines throughout the house.
What drives that choice
Pipe age and material matter first. Old galvanized pipe and aging copper both reach a point where one leak means more are on the way. Where the leak sits matters too. An easy-to-reach leak under a closet or utility room floor makes a good spot repair. One under a kitchen island, or a hardwood floor you’d hate to tear up, makes a reroute look a lot better. And how many leaks turn up during testing changes the math. One leak in copper installed ten years ago is a different job than three leaks in pipe that’s forty years old.
What about insurance?
Some homeowner’s policies cover the cost of accessing the pipe and repairing the damage to floors and walls, but not the pipe itself. Others draw the line differently. Check your policy or call your insurer before you assume either way. We can tell you what the leak and the repair look like, not what your coverage says.
If any of these signs sound familiar, get the meter test done first. If it points to a leak and you’d rather hand it off than start locating it yourself, here’s how our leak detection service works.