Seven signs of a slab leak in an Elgin home

The short answer

The short answer

The most reliable indicator is the water meter: shut every fixture off, watch the meter's low-flow dial for fifteen minutes, and if it moves you have a leak somewhere in the system. A warm patch on a tile floor, an unexplained bill increase, and the sound of running water in a quiet house are the next most reliable.

Why this is an Elgin problem

Homes here are overwhelmingly built on concrete slab rather than over a crawlspace, and in the tracts that went up from the 1950s through the 1970s the copper supply lines run inside or beneath that slab. When a pinhole opens, there is no basement for the water to show up in — it goes into the ground, or it works its way up through the concrete.

That is the whole difficulty. A leak under a sink announces itself in a day. A leak under a slab can run for months before anything visible happens.

The seven signs, most reliable first

1. The meter moves with everything off. Near-definitive. Find your meter at the street, close every faucet and valve, do not run the irrigation, and watch the small triangular or gear-shaped low-flow indicator. Movement means water is leaving the system somewhere.

2. A water bill that jumped without a reason. Compare against the same month last year, not last month — irrigation seasonality will mislead you otherwise.

3. A warm spot on the floor. Specific to hot-water-side leaks and very telling when you feel it. Tile shows it most clearly; carpet hides it.

4. Running water you can hear in a silent house. Late at night, with everything off. A faint continuous hiss or trickle with no source.

5. Low water pressure that came on gradually. On its own this is more often aging galvanized pipe than a slab leak, but combined with any of the above it points the same direction.

6. Cracks appearing in flooring or drywall. Water under a slab moves soil. Moving soil moves the slab. This is a late sign.

7. A musty smell or unexplained damp carpet edge. Also late — by the time moisture is surfacing it has been running a while.

What we do when you call

We confirm there is a leak before we go looking for it, using the meter and a pressure test to isolate hot side from cold side. That step matters: it prevents an expensive search for something that turns out to be an irrigation valve.

Then it is acoustic listening equipment and thermal imaging to narrow the location to within a foot or so before anything gets opened. The point of good leak detection is to make the repair small.

Repair options depend on the pipe's age and history. A single pinhole in otherwise healthy copper gets a spot repair. A line that has already leaked twice gets rerouted overhead instead, because a third pinhole is coming. Our slab leak repair page lays out how we choose.

What to do tonight if you suspect one

Do the meter test. It takes fifteen minutes, costs nothing, and it is the same first step we would take. If the dial moves, shut the main off at the street until someone can look at it — a slab leak does not get better overnight, and the soil damage is cumulative.

If it does not move, you have ruled out the expensive possibility, and the warm floor is probably a sunlit patch or a heating duct.