A slab leak is a leak in a water pipe running underneath a home's concrete foundation. Because the pipe is buried under the slab, the leak is hidden from view and can run for a long time before it's discovered through indirect signs like a high water bill or warm flooring.

Finding Hidden Leaks · Published August 19, 2026

Can You Detect a Water Leak Under Concrete? Slab Leaks Explained

Q: How does slab leak detection work?

Detection typically starts with a water meter test to confirm a leak exists somewhere on the property. If it points underneath the slab, professionals use acoustic listening devices to hear the sound of escaping water through the concrete, or thermal imaging to spot temperature differences from hot water lines, without having to dig or break up the floor to find it.

Q: Will a slab leak show up on the water meter?

Yes — a simple water meter test is the standard first step and can be done by any homeowner for free. Turn off all water use in the house, note the meter reading, wait 1-2 hours without using any water, then check again. Any movement means water is flowing somewhere, which points toward a leak even before you know exactly where.

Q: Are slab leaks covered by insurance?

Often the water damage a slab leak causes is covered if it's sudden and accidental, but the cost of detecting and repairing the pipe itself is usually considered maintenance and excluded, similar to how most leak repairs work under a standard homeowners policy.

Yes — slab leaks are detectable, and the first diagnostic step is free and takes about an hour. Here's how to check it yourself, how professionals confirm and pinpoint it if you need them, and what it actually costs.

By the DryLine Home Team — background in water damage restoration

Key takeaways

The water meter test is free and the right first step — anyone can do it before calling a professional.
Warm or consistently damp flooring is the most reliable physical sign, alongside an unexplained water bill spike.
Professionals use acoustic and thermal detection — genuinely not something meaningfully DIY-able once you're past the meter test.
Detection alone typically runs $150–$600 (averaging around $250–$280); full repair including detection is usually $1,500–$4,500.
Detection and repair are billed separately — insurance treatment differs between the two, which trips a lot of people up.

What is a slab leak, actually

Most homes built on a concrete slab foundation run their water supply lines underneath that slab rather than through accessible walls. When one of those buried pipes corrodes, cracks, or fails at a joint, the resulting leak has nowhere visible to show up — it seeps into the ground and the concrete itself rather than dripping somewhere you'd notice right away. That's what makes slab leaks different from an under-sink leak or a burst washing machine hose: by the time there's an obvious sign, the leak has often been running for a while.

The water meter test — do this first, it's free

This is the single most useful thing a homeowner can do before spending money on anything else. Turn off every fixture and appliance that uses water — no dishwasher, no washing machine, nobody flushing a toilet. Find your water meter and note the reading exactly. Wait one to two hours without using any water at all, then check the meter again.

Any movement in that reading means water is flowing somewhere in your system while nothing should be running. That doesn't confirm a slab leak specifically — it could be a leak anywhere on the property side of the meter — but it's the fastest, cheapest way to establish that a leak exists at all before you spend money finding out exactly where.

Warning signs beyond the meter test

Warm or hot spots on the floor — a strong indicator if the leak is on a hot water line, since it effectively turns a patch of your slab into radiant heating you never asked for.
An unexplained spike in your water bill — especially if your usage habits haven't changed.
The sound of running water when nothing's on — easiest to notice in a quiet house at night.
Damp carpet, baseboards, or flooring with no obvious external cause like a spill or a window leak.
Cracks in flooring or walls that develop over time, which can indicate the leak has been running long enough to affect the foundation itself.

How professional slab leak detection actually works

Once the meter test points to a leak, pinpointing its exact location under the slab is a job for specialized equipment — this is genuinely not a DIY step. Plumbers and leak detection specialists typically use one or both of two non-invasive methods:

Acoustic detection uses sensitive listening equipment to pick up the specific sound signature of pressurized water escaping through a pipe, transmitted through the concrete. A trained technician can often pinpoint the leak's location within a small radius just from where that sound is loudest.

Thermal imaging works especially well for hot water line leaks, since the escaping hot water raises the surface temperature of the concrete directly above it just enough for an infrared camera to pick up, without any digging or demolition.

Both methods exist specifically to avoid the alternative — breaking up sections of the slab to search for the leak by trial and error, which is far more expensive and disruptive than it needs to be with modern detection equipment.

What it costs

Detection and repair are two separate costs, and pricing data from Angi and CostHelper puts them in different ranges. Professional slab leak detection alone typically runs $150 to $600, averaging around $250 to $280 for a standard job — that figure covers locating the leak, not fixing it. Full slab leak repair, including detection, typically runs $1,500 to $4,500 for most homes, and can run higher if the leak is hard to access or the repair method requires more extensive foundation work.

Get more than one quote if the cost matters to your decision — pricing varies meaningfully by region and by which method a given company defaults to.

Is a slab leak covered by insurance?

This is where the detection-versus-repair distinction really matters. The water damage a slab leak causes — warped flooring, damaged drywall, mold from prolonged moisture — is often covered by a standard homeowners policy if it's treated as sudden and accidental. But the cost of actually detecting and repairing the pipe itself is typically excluded, treated the same way as any other plumbing maintenance. See our breakdown of what leak detection insurance actually covers for the fuller picture, since this split trips up almost everyone who hasn't dealt with a claim before.

FAQ

Common questions

What is a slab leak?

A leak in a water pipe running underneath a home's concrete foundation, hidden from view and often discovered through indirect signs rather than a visible drip.

How does slab leak detection work?

Starts with a free water meter test, then acoustic listening or thermal imaging equipment to pinpoint the exact location without digging.

How much does slab leak detection cost?

Typically $150–$600, averaging around $250–$280, separate from repair costs of $1,500–$4,500.

Will a slab leak show up on the water meter?

Yes — a simple meter test (shut off all water, check the meter, wait, check again) is the standard free first step anyone can do.

Are slab leaks covered by insurance?

Often the resulting water damage is, if sudden and accidental — but detection and repair of the pipe itself is usually treated as maintenance and excluded.