Professionals find hidden slab leaks by listening for them and by reading heat. Acoustic gear picks up the sound of water escaping a pressurized pipe under the concrete, and a thermal camera shows where a hot water line is warming the floor. No jackhammering around hoping to get lucky. Below, we walk through how the equipment works, what a slab leak looks like from inside, and why finding one early matters for your wallet.
Acoustic and Thermal Detection: How Slab Leaks Are Located
Slab leaks are located with two main tools. Acoustic equipment listens for the hiss of pressurized water escaping a pipe beneath the concrete, and thermal imaging picks up warm spots on the floor above a leaking hot water line. Between them, a technician can usually narrow the leak down to a small patch of floor.
First, though, we make sure there’s actually a leak. Our tech shuts off every fixture and watches the meter. If that little dial keeps turning, water is going somewhere. Pressure testing comes next, one line at a time, so we know if it’s the hot side, the cold side, or (occasionally) both.
Then the listening starts. A leak detection specialist sets a ground microphone on the floor and moves it a little at a time. Water squeezing out of a crack makes a hiss you’d never hear from the kitchen, but through the headphones it gets louder as the mic gets closer. On a hot line, you can actually watch the heat bloom across the tile on the thermal camera’s screen.
It sounds fussy. It is. But a precise mark means we cut one small opening instead of pulling up a whole hallway of tile.
Slab Leak Detection Methods Compared
| Method | What It Does | Best Used For |
|---|---|---|
| Water meter test | Shows water moving with everything off | Confirming there’s a leak |
| Pressure testing | Checks if each line holds pressure | Telling hot lines from cold |
| Acoustic detection | Amplifies the sound of escaping water | Pinpointing leaks under concrete |
| Thermal imaging | Shows temperature changes on the floor | Tracking leaking hot water lines |
Warning Signs of a Slab Leak Under Your Foundation
The usual warning signs of a slab leak under your foundation are a water bill that jumps for no reason, the sound of water running when nothing is on, a warm or damp spot on the floor, and cracks showing up in tile or drywall. A water heater that seems to run all the time is another clue.
A lot of people catch it on the bill first. Your usage hasn’t changed, nobody’s taking longer showers, and yet the number keeps climbing. That water has to be going somewhere, and in a slab home, the concrete is a common place for it to vanish. Then the house starts dropping hints:
- A spot on the tile that feels warm under bare feet, usually right over a hot water line
- Carpet that’s damp in one corner, or a musty smell you can’t track down
- Cracks in baseboards, drywall, or grout that weren’t there last month
- Weak water pressure everywhere, not just at one faucet
Plenty of Jacksonville homes built before 1990 still have their original supply lines under the slab, and those pipes have been quietly corroding for decades. A water leak in concrete slab floor sections won’t stop on its own, either. A foundation leak just keeps soaking the soil under your house until someone finds it, so if any of this sounds familiar, book foundation leak detection sooner rather than later.
Why Early Slab Leak Detection Saves Homeowners Money
Early slab leak detection saves homeowners money because a small leak is a small repair. Caught quickly, it’s usually one opening and one fixed section of pipe. Left alone for months, the same leak can wash out soil under the foundation, ruin flooring, and grow mold, and by then you’re paying for restoration, not just plumbing.
You’re also paying for the water itself. Every gallon going into the ground runs through your meter first. Honestly, though, the soil erosion is the part that worries us most. Pipes are fixable. Foundation problems are a much bigger headache.
Once our leak detection services find the problem, there are usually two ways to go:
- A direct slab water leak repair through a small opening in the floor (best when the rest of the pipe is healthy)
- Rerouting the line above the slab through the walls or attic, so the concrete stays put
Good residential leak detection services also save you from demolition you never needed. Under slab plumbing repair and foundation plumbing repair both go faster when the crew knows exactly where to cut. If leaks keep coming back, though, repiping may make more sense than one more foundation leak repair. We’ll tell you honestly which camp you’re in.
Timing matters, too, so pick a water leak detection company that actually answers at night. Our water leak detection services and under slab leak repair crew work 24/7, so a leak you spot Saturday night doesn’t sit there soaking the slab until Monday.
Frequently Asked Questions
Can I check for a slab leak myself before calling a plumber?
You can, and it doesn’t take much effort. Turn off every faucet, the dishwasher, the washing machine, and the sprinklers. Write down the number on your water meter, leave everything off for an hour or two, and check again. If the number moved, you’ve got a leak somewhere. The test can’t tell you whether it’s under the slab or inside a wall, but it’s a good reason to call for proper leak detection.
Will my floors be torn up during slab leak detection?
No. Finding the leak doesn’t involve cutting anything. The acoustic gear listens right through the concrete and flooring, and the thermal camera only reads surface temperature. Flooring comes up only during the repair, and even then we’ll go over your options and give you a quote first. In some cases, rerouting the pipe means the slab never gets opened at all, which most homeowners are pretty happy to hear.
What causes slab leaks in Jacksonville homes?
In our experience, it usually comes down to age. Homes built before 1990 often still have their original pipes under the foundation, and after decades of water moving through them, the metal wears down. Soil shifting under the house puts stress on those lines, too. Sometimes a pipe has been rubbing against concrete or gravel for years until it wears through, and now and then the original installation just wasn’t great. Once the leak is exposed, the technician can usually tell you which it was.
Is it better to repair a slab leak directly or reroute the pipe?
That depends on the pipe. If the line is in decent shape and the leak is somewhere we can reach easily, a direct repair is the simple fix. Rerouting starts to make more sense when the pipe is old, when the leak sits under flooring you really don’t want disturbed, or when other sections look like they’re next in line. We’ll show you what we found and talk through both options before anything gets touched.
What should I do right after I suspect a slab leak?
Shut off your main water valve first. That keeps the damage from getting worse while you figure out next steps. Pull rugs and furniture away from any damp areas, then give us a call. Sweeney Plumbing & Electric runs 24/7 emergency service across the Jacksonville metro, with an average response time of 45 to 60 minutes. If you can’t find your main shut-off, our dispatcher can help you locate it over the phone.