Slab leak signs: how to tell, and what to do next
A slab leak is a leak in a water line under a concrete floor. You can't see the pipe, so you notice the side effects first. One sign alone can have another cause. Two or more together are worth checking.
Signs to look for
- A warm spot on the floor, often over a hot-water line. Bare feet notice it first on tile.
- A water bill that jumps with no change in how you use water.
- Running water you can hear when every tap and appliance is off.
- A sudden change in water pressure around the house.
- New cracks in the slab or foundation.
- Damp carpet, lifting flooring or a musty smell in a room with no fixtures.
HomeGuide lists the first five as common slab leak signs (HomeGuide, Checked Oct 12, 2026). For leaks that could be anywhere in the house, see 10 signs of a hidden water leak.
Confirm there is a leak: the meter test
Before you pay anyone, check the water meter. The EPA suggests reading it before and after a two-hour period when no water is used. If it changes at all, you probably have a leak (EPA WaterSense, Checked Oct 12, 2026). Our step-by-step meter test also shows how to tell an outdoor service-line leak from one inside the house.
How pros find a leak under concrete
The goal of leak detection is to find the spot before anyone breaks the floor. A plumber or leak detection company usually starts by pressure-testing the lines to confirm which one is losing water, then narrows it down, often with acoustic listening or thermal imaging. See how professional leak detection works.
Fixr puts a slab leak detection test at $100 to $400 nationally (Fixr, national, Checked Oct 12, 2026).
The three usual repairs
- Direct access: open the slab at the leak, repair or replace that section of pipe, then patch the concrete. HomeGuide's national range for digging and replacing pipes is $700 to $5,000 (HomeGuide, national, Checked Oct 12, 2026).
- Reroute: cap the old line and run new pipe through walls or the attic instead of under the slab. HomeGuide's national range is $3,900 to $7,500 (HomeGuide, national, Checked Oct 12, 2026).
- Pipe lining: coat the inside of the damaged pipe without digging. HomeGuide's national range is $500 to $3,500 (HomeGuide, national, Checked Oct 12, 2026).
Fixr gives a national average range of $1,000 to $4,000 for slab leak repair (Fixr, national, Checked Oct 12, 2026). These are national figures from cost guides, not local quotes. For a fuller price breakdown, our sister site has a slab leak repair cost guide.
Questions to ask before you agree to the work
- Which line is leaking, hot or cold, and how was it confirmed?
- Can you mark the leak location and show me the test results?
- Why this repair (direct access, reroute or lining) over the others?
- Does the written estimate include patching the concrete, replacing flooring, debris removal and permits?
- If one leak is found on an old line, how likely is another, and would a reroute avoid that?
- What is the written warranty on the repair?
HomeGuide also suggests getting at least 3 in-person estimates and being wary of anyone who recommends replacing the whole slab without a thorough inspection (HomeGuide, Checked Oct 12, 2026).
FAQ
What is a slab leak?
A leak in a water pipe that runs under a concrete slab foundation, or a crack in the slab that lets moisture in. HomeGuide lists corroded metal pipe, heat or pressure stress, weak points in plastic or PEX pipe, and hard or acidic water as common causes (HomeGuide, Checked Oct 12, 2026).
How do you know if you have a slab leak?
Look for two or more signs together: a water bill that jumps without a change in use, a warm spot on the floor, the sound of running water with everything off, a sudden change in water pressure, or new cracks in the slab. Then run a meter test with all water off. If the meter still moves, call for leak detection.
How much does slab leak detection cost?
Fixr puts a slab leak detection test at $100 to $400 nationally, depending on how invasive it needs to be (Fixr, national, Checked Oct 12, 2026). Local prices vary, so ask for the price in writing first.
Is a slab leak covered by homeowners insurance?
Often not, and it depends on your policy. Fixr says slab leaks are not covered in most cases and suggests calling your insurer first (Fixr, Checked Oct 12, 2026). The Texas Department of Insurance lists damage to foundations or slabs as a common add-on endorsement (Texas Department of Insurance, Checked Oct 12, 2026). Read your own policy before work starts.
How long does a slab leak repair take?
HomeGuide says plumbers can usually fix a slab leak in 1 to 3 days, and longer if flooring or cabinets also need replacing (HomeGuide, Checked Oct 12, 2026).
Sources
- HomeGuide: How Much Does a Slab Leak Repair Cost? (2026), Oct 29, 2025 (national), Checked Oct 12, 2026
- Fixr: Slab Leak Repair Cost, updated May 1, 2025 (national), Checked Oct 12, 2026
- US EPA WaterSense: Fix a Leak Week, Checked Oct 12, 2026
- Texas Department of Insurance: Home insurance guide, Checked Oct 12, 2026
Prices are national figures from published cost guides, not local quotes. Always get written quotes. This page is general information, not professional or insurance advice.