The six signs, and what each one actually means
These are listed roughly in order of how conclusive they are. The first three are worth a call on their own.
- A warm patch on the floor. The most specific sign there is. Tile or wood that is noticeably warm in one spot, with no heating vent under it, means a hot line is leaking directly beneath.
- The bill up 20-40% with nothing changed. A slab leak runs constantly. Compare against the same month last year rather than last month — summer irrigation hides a lot.
- Water moving with everything off. Shut every fixture, stand still in a quiet hallway, and listen. A faint hiss or trickle from below is not the house settling.
- Damp carpet, cupped flooring, or a musty smell that keeps coming back in the same room after cleaning.
- New cracks in tile, drywall or the foundation itself. Water washing soil out from under a slab lets that section settle.
- Pressure down throughout the house — every fixture, not just one. A single weak faucet is an aerator; the whole house is supply.
Worth knowing
One sign on its own can have an innocent explanation. Two or three together rarely do. If the warm-patch sign is present, treat it as confirmed until proven otherwise — it is the one that almost never has another cause.
Why the ground here is unusually hard on buried pipe
Hill Country soil carries a lot of expansive clay. Clay takes on water and swells, then dries out and shrinks — and our weather runs that cycle hard, with long dry summers broken by heavy rain.
A slab sitting on that soil does not move as one piece. Different parts of it lift and settle by different amounts through the year. Anything rigid running through or beneath the concrete has to absorb that movement, and copper tubing is the least forgiving thing down there.
The hot lines fail first for a second reason on top of the soil. Copper expands as it heats and contracts as it cools, every time anyone runs hot water — several thousand cycles a year. Where the line touches concrete or rebar, that movement abrades it. Over enough years it wears through from the outside, which is why a slab leak is usually a pinhole rather than a burst.
How a leak gets located before anything is opened
The point of detection is to open the smallest hole possible, in the right place, once. Guessing is what turns a slab leak into a demolition project.
The house is isolated section by section under pressure first, which establishes that the leak is on the supply side and narrows it to hot or cold. Acoustic equipment then listens through the slab for the specific sound pressurised water makes escaping a small opening. Thermal scanning helps on hot-line leaks, because the warm patch that you can feel with a bare foot shows up far more precisely on camera.
Between those, the leak can usually be placed within a small area before a single tool touches the floor.
The three repair options, honestly compared
Which one is right depends on the age of the pipe, how many leaks the house has had, and where in the slab the fault sits.
Spot repair. Open the floor at the leak, cut out the failed section, replace it. Cheapest and quickest, and the right answer for a young system with one fault. The catch: if the pipe failed because of what the soil is doing, the rest of that run is the same age under the same conditions.
Reroute. Abandon the failed line in the slab and run a new one overhead through the attic and down the walls. Costs more and involves drywall work, but it takes that run permanently out of the ground. Usually the right call on a second leak in the same house.
Full repipe. Replace the whole system above the slab. It is the largest job here and nobody chooses it lightly, but for a house on its third or fourth leak it is cheaper than the next three spot repairs and the floor damage that comes with them.
We will tell you which of these your house actually needs, including when the answer is the cheap one.
What to do before anyone arrives
If you can hear water moving and you can see damage, shut the main off at the meter. That stops the loss immediately, and you can turn it back on when you need water.
If the sign is a warm floor and a high bill but nothing is visibly wet, there is no emergency in the next few hours — but there is one in the next few weeks. A leak under a slab does not stay the same size, and the expensive part is rarely the pipe. It is what the escaping water does to the soil holding the foundation up.
Photograph the floor, keep the last two bills, and note when you first noticed it. All three help place the leak faster.