Slab leak detection
A slab leak is a break in a pipe running beneath your home's concrete foundation. It can run for months before you see anything.
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Signs of a slab leak
- A warm or hot spot on the floor (a hot water line leak)
- The sound of running water when everything is off
- A water bill that jumped with no change in usage
- Cracks appearing in floors or walls
- Damp carpet or warped flooring with no obvious source
- A persistent musty smell or visible mold at floor level
- Water pressure dropping across the house
- The foundation shifting or floors becoming uneven
The meter test — do this before calling anyone
It takes fifteen minutes and gives a plumber real information:
- Turn off every water-using fixture and appliance in the house, including ice makers and irrigation.
- Find your water meter and note the exact reading, or watch the small leak-indicator dial or triangle.
- Wait fifteen to thirty minutes without using any water.
- Check again. Movement means water is going somewhere — you have a leak.
- To narrow it: close the main shutoff at the house and repeat. If the meter still moves, the leak is between the meter and the house. If it stops, the leak is inside.
It proves you have a leak somewhere. It could be an irrigation line, a toilet flapper leaking silently into the bowl, or a supply line under a sink. Rule those out first — a running toilet is by far the most common cause of a mysteriously high water bill, and it's a $12 part.
How leaks under a slab are located
Plumbers use acoustic listening equipment, electronic amplification, thermal imaging (very effective on hot water lines), and tracer gas — pressurizing the line with an inert gas and detecting where it surfaces. Good detection is what keeps the repair small, so it's worth paying for properly.
| Repair option | What it involves | Typical cost |
|---|---|---|
| Spot repair | Break through the slab at the leak, repair, re-pour. Cheapest if the leak is accessible and isolated | $1,500–$4,000 |
| Reroute | Abandon the pipe under the slab and run a new line through walls or the attic. Avoids further slab work | $1,500–$5,000 |
| Epoxy pipe lining | Coat the inside of existing pipe. No demolition, but not suitable for every situation | $4,000–$10,000 |
| Full repipe | Replace the whole system, usually overhead. Right answer when there have been multiple leaks | $5,000–$20,000+ |
| Detection only | Locating the leak, often credited toward repair | $150–$600 |
A single slab leak in an otherwise healthy system is usually a spot repair. Two or more in a couple of years means the piping itself is failing — often thin-wall copper in aggressive soil — and repeated spot repairs become throwing money at it. That's the point where a reroute or repipe is genuinely the cheaper decision.
Frequently asked questions
How much does slab leak repair cost?
Detection typically $150–$600. Spot repair $1,500–$4,000. Rerouting the line $1,500–$5,000. Full repipe $5,000–$20,000+. Location and accessibility drive most of the variation.
Does homeowners insurance cover slab leaks?
Many policies cover the resulting damage — and specifically the cost of breaking through and repairing the slab to access the pipe — while excluding the pipe repair itself. Coverage varies a lot between policies. Read yours and talk to your insurer before authorizing work.
Can a slab leak be repaired without breaking the floor?
Often yes. Rerouting the affected line overhead or through walls avoids slab work entirely and is frequently cheaper than excavation. Epoxy lining is another no-demolition option in some situations. Ask about both before agreeing to break concrete.
How urgent is a slab leak?
Not a same-hour emergency in most cases, but not something to defer either. Water under a foundation erodes supporting soil, and prolonged leaks cause foundation movement — which costs vastly more than the plumbing. Weeks, not months.
Plumbing emergency right now?
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Call (888) 876-3092PlumbLinker is a referral service. We connect you with independent licensed plumbers — we do not perform plumbing work ourselves.