Slab Leak Water Damage
A slab leak is a pressurised water line failing underneath the concrete your house sits on. Nothing drips from a ceiling and there is no puddle to point at, which is exactly why they run for months. In Houston they are common, because almost every house here is built on a slab and the clay underneath it never stops moving.
The five-minute test that tells you for certain
Before you call anyone, do this. It costs nothing and it answers the question.
- Turn everything off. Every tap, the ice maker, the irrigation, the washing machine, the pool auto-fill. Nothing in the house should be using water.
- Find the meter. It is in a box in the ground near the street, usually under a concrete or plastic lid.
- Watch the leak indicator. Most meters have a small triangle, star or dial that spins at the slightest flow. If it is moving with everything off, water is escaping somewhere.
- Close the main shut-off at the house and watch again. If the indicator stops, the leak is inside or under the house. If it keeps turning, the leak is out in the yard between the meter and the house.
- Photograph the meter reading and note the time. Take another reading two hours later. That difference tells you roughly how fast water is escaping, and it is the most useful single number you can hand a plumber.
- Call a licensed plumber to locate and repair it, and call us for the water inside the house. They are two different jobs and neither company should pretend to do both.
Why Houston gets so many of them
Two local facts stack up against you. The first is that we build on slabs. No basements, no crawl spaces in most of the region, so the supply lines run through or under the concrete. The second is the soil. Southeast Texas clay is highly expansive: it swells when it is wet and shrinks hard when it dries, and it does that seasonally, every year. Anything buried in it gets moved.
That movement works on the pipes. Older copper supply lines abrade where they pass through the slab or rub against aggregate, and the hot-side line goes first more often than not, because heat and movement together are harder on copper than either alone. The result is a pinhole, not a burst, which is why the leak is slow and silent and expensive by the time anyone notices.
The signs, in roughly the order people notice them
| What you notice | What it means |
|---|---|
| A warm patch on the floor | The classic hot-side slab leak. A distinct warm area on tile or wood, often in a hallway or near a bathroom, with no heating source above or below it. |
| Running water with nothing on | A faint hiss or trickle audible in a quiet house, usually best heard at floor level or with an ear to a tiled floor. |
| The water bill jumps | A pinhole leaking continuously can add thousands of gallons a month. Many Houston-area utilities will flag an unusual jump, but not always quickly. |
| Baseboards wicking | Paint bubbling or trim swelling along the bottom of one wall, often before anything shows on the floor itself. Water travels along the slab and climbs the wall base. |
| Flooring lifting with no source | Wood cupping or laminate swelling in a patch, or tile grout darkening and tiles going hollow-sounding, with nothing above that could have spilled. |
| A musty smell along one wall | Wall cavity moisture. By the time you can smell it, it has been wet long enough for growth to start. |
| New cracks, sticking doors | Later-stage. Saturated soil under one part of the house moves differently from dry soil under the rest, and the structure follows. |
If you have a warm floor patch and a spinning meter dial, you do not need a leak detection service to tell you that you have a problem. You need one to tell you exactly where, which is worth paying for, because it is the difference between a targeted repair and a hopeful one.
Two companies, two jobs
This is the part that causes the most confusion, so here it is plainly.
We will coordinate with your plumber rather than wait for them. Drying can often start before the repair is finished, as long as the water is shut off, and starting early is what keeps the job small.
Why drying a slab is its own problem
Drywall gives up its moisture quickly. Concrete does not. It absorbs water slowly, holds a great deal of it, and releases it slowly for a long time afterwards, which is why a slab leak job has a different shape from a burst pipe job.
Water goes sideways, then up
Water spreading under and across a slab does not stay where the pipe failed. It travels along the top of the slab under the flooring, reaches the wall base, and wicks up into the bottom plate, the insulation and the drywall. So the wet area is typically defined at the wall line and in the cavities, not by where the floor looks damp.
What the drying actually involves
| Stage | What it involves |
|---|---|
| 1. Map | Moisture readings across flooring, slab, wall bases and cavities, with a dry reference reading elsewhere in the house. Non-invasive first, then pin readings to confirm depth. |
| 2. Open the wall base | Base trim off, and small inspection or weep holes at the plate line where readings call for them, so the cavity can be dried rather than sealed wet behind paint. |
| 3. Lift what has to come up | Carpet and pad almost always. Laminate almost always. Engineered and solid wood over slab is the hard case and usually comes up. Tile on a well-bonded bed can often stay, and we will tell you which one you have rather than defaulting to removal. |
| 4. Cavity and slab drying | Directed airflow into wall cavities, and a contained drying chamber with dehumidification sized to the volume. Closed system, because Houston outdoor air is usually wetter than the air being dried. |
| 5. Daily readings | Logged every day against the reference until materials reach dry standard. Slabs are the reason this matters; surface dry and dry are very different things on concrete. |
| 6. Hand over | Full documentation package: readings, sketch, photographs, daily logs and the written scope, in a form you and your flooring contractor can both work from. |
Expect five to ten days of equipment for a typical one or two room slab leak, and longer where the leak ran for months or where wood flooring is involved. Anyone quoting you three days without having taken a reading is quoting a calendar, not a house.
Questions people ask us on this call
Can you find the leak for me?
Locating and repairing a leak under a slab is licensed plumbing work, and that is who should do it. We are the water and structure side: extraction, drying the slab and the walls, and documentation. What we can do on day one is confirm how far the water has actually travelled through the house, which is usually further than the plumber’s access point suggests, and get drying started so you are not waiting on the repair before anything happens.
Will a slab leak damage my foundation?
Not usually in the way people fear. The real risk in Houston is the soil, not the concrete. Our clay shrinks and swells dramatically with moisture, so a leak that has been saturating the ground under one corner of the house for months can cause differential movement, which shows up as sticking doors and cracks. A leak caught in weeks rather than months rarely gets that far. If you are seeing new structural cracking, a structural engineer is the right person to ask, not a restoration contractor.
How do I know it is a slab leak and not the air conditioner?
A slab leak does not care whether the AC is running, and its water comes up from the floor rather than down from the ceiling. If the wet area starts at a baseboard and the floor is warm in a patch, look under the slab. If the stain is on the ceiling and worsens when the system runs, look at the condensate drain instead.
How long does it take to dry a slab?
Longer than drywall. Surface moisture and wet wall bases typically come down in five to ten days. Concrete that has been saturated for months releases moisture for weeks afterwards, which is why we set a dry standard against a reference reading and why anyone who promises a finished floor three days after a slab leak has not measured it.
Do I have to move out?
Usually not. Most slab leak jobs are one or two rooms and a hallway, and people stay. The equipment is loud and the house runs warmer than normal with the dehumidifiers going. If a kitchen is out of action, or someone in the house does not cope well with the noise and heat, moving out for a few days is a perfectly reasonable thing to do.
Can I wait and see if it gets worse?
The meter running while nothing is on has already told you it will. A slab leak does not heal, the water bill keeps climbing, and every week of saturated soil and wicking walls adds to the eventual repair. The cheapest version of this job is the one that starts soonest.
Keep reading
Spinning meter, warm floor, rising bill?
Tell us what you have found and we will tell you what we would do next, including when the honest answer is to call a plumber first and us second.