Slab leak detection: how the leak is actually found
Knowing you have a slab leak and knowing where it is are two different problems. The second one is what keeps the repair from turning into a demolition.
Signs to look for
- You already know there is a leak but not where
- A plumber has confirmed pressure loss on the supply side
- Damage is showing in one room but the source could be anywhere
- You want the location documented before anyone opens the floor
Several of these signs also fit something above the slab, and one free check separates them better than a list can. The slab leak check asks what you are seeing, what the water meter does with everything shut off, and where the sign sits.
- 1 AC condensate. The pan overflows up in the attic and finds the ceiling below it.
- 2 The ceiling stain. It marks where the water arrived, not where it started out.
- 3 A burst supply line. Pressurized pipe inside a wall, running until the main is shut.
- 4 The water heater. Often in the garage, and its failure runs toward the house, not away from it.
- 5 A slab leak. It travels sideways under the concrete and surfaces long after it began.
The methods, and what each one is good at
Pressure testing isolates the system to confirm the leak is on the supply side rather than a drain. It answers whether, not where.
Acoustic listening equipment picks up the sound of water escaping under pressure through concrete. It is the primary locating method and it is why the house needs to be quiet during the work.
Thermal imaging reads temperature differences through the floor: useful when the leak is on a hot water line, because the escaping water heats the slab above it.
Tracer gas is the fallback when the others are inconclusive: an inert gas is introduced into the line and detected where it surfaces through the concrete.
Why locating first saves money
The alternative to locating is opening the floor until the leak appears. On a tile or hardwood floor, that is often more expensive than the plumbing repair itself.
Fixing the source is only half of it
Detection tells you where the pipe failed. It also tells you how far the water travelled, and that second number is the one that decides how much of the floor and wall assembly needs to be dried rather than simply patched.