Quick answer
A slab leak is a leak in a water pipe under or inside a concrete slab. Warning signs include an unexplained jump in the water bill, the sound of running water when everything is off, warm spots on the floor and damp carpet or cracks. Shut off the water and call a leak detection plumber.
What a slab leak is
Many Arizona homes are built on concrete slab foundations with plumbing running through or beneath the slab. If one of those lines corrodes or wears through, water leaks into the soil and slab. Because the pipe is hidden, a slab leak can run for weeks or months before anyone notices.
Common warning signs
- A water bill that jumps without any change in how you use water
- The sound of running water when all fixtures and appliances are off
- A warm or hot spot on a floor, which can indicate a hot water line leak
- Damp or wet carpet, flooring that warps or lifts, or tile that cracks
- Lower water pressure than usual
- A musty smell with no visible source
- Water around the foundation outside the house
- Cracks in walls or the slab
A simple meter test
Turn off every faucet and appliance that uses water, including the ice maker and irrigation. Look at the water meter. If the leak indicator or the dial is moving, water is going somewhere. If you also shut off the main valve at the house and the meter stops, the leak is on the house side. Many plumbers can then pinpoint the exact location with acoustic and electronic leak detection.
Why slab leaks happen
- Corrosion in older copper pipe, accelerated by water chemistry and soil conditions
- Pipes rubbing against concrete or gravel as the house settles and the pipe expands and contracts with temperature
- High water pressure
- Poor installation
What to do
- Shut off the main water valve if you suspect a leak or see water.
- Call a plumber who does leak detection. Ask them to confirm the location before any work.
- Call a restoration company if flooring, drywall or baseboards are wet. A slab leak can soak the whole floor system.
- Call your insurer. Coverage for slab leaks depends on the policy, the cause and whether the damage was sudden or gradual.
Repair options
Plumbers commonly offer spot repair by breaking through the slab, rerouting the line through walls or the attic, or lining the pipe. The right choice depends on the pipe, the number of leaks and how old the plumbing is. Get more than one opinion for large jobs.
Frequently asked questions
Can a slab leak damage the foundation?
A long running leak can wash out soil under the slab and, in some soils, contribute to movement or cracking. Fixing it early limits that risk.
Does homeowners insurance cover slab leaks?
It depends on the policy. Many cover the resulting water damage if the leak was sudden and accidental but not the cost of accessing and repairing the pipe. Gradual leaks are often excluded. Ask your insurer before work starts.