How Professionals Locate Leaks Under a Concrete Slab

Step 1: Confirm water loss

Everything starts with evidence. A meter test with all water off confirms whether water is actually being lost. Without that confirmation, every later step is built on sand.

Step 2: Rule out fixtures

Toilets, dripping taps, irrigation and water-using appliances are checked, because each can imitate a slab leak on the meter. Many 'slab leaks' end here, solved as a toilet flapper.

Step 3: Isolate the line

Hot and cold lines are separated using the water heater valve and other shut-offs. If the meter stops when the hot side is closed, the search narrows to the hot-water lines — and hot lines announce themselves through warm floor spots, which thermal imaging maps well.

Step 4: Trace and pinpoint

With the line identified, its likely route is traced and the pinpointing method is chosen for the conditions: acoustic listening for pressurised leaks with a clear sound, thermal imaging for hot lines, and tracer gas for quiet, deep or plastic-pipe leaks. Findings are cross-checked where possible, because every method has conditions that can mislead it.

• Acoustic: fast and precise when the leak is audible
• Thermal: ideal for hot-water lines under flooring
• Tracer gas: for small, deep or silent leaks

Step 5: Explain the finding — and the uncertainty

A professional result states where the leak is, which line it is on, and how confident the evidence makes that conclusion. Detection and repair are then planned separately: options may include a spot opening at the located point, rerouting the line overhead, or other routes — each with different cost and disruption, explained before you choose.

Frequently asked questions

Need help with this at your property? See Slab Leak Detection or request leak detection service.