If you suspect a leak under a concrete slab, stop using water, check the water meter and limit further damage. Turn off the property’s water supply if water is actively escaping or damage is worsening, provided the main shut-off valve is safely accessible. Avoid breaking the concrete and arrange an assessment by a licensed plumber.
Immediate steps
- Stop water use: Turn off taps, irrigation and water-using appliances. Check that toilets are not refilling and automatic appliances are inactive.
- Document visible damage: Photograph pooling or damp areas. These signs do not confirm where the leak is located.
- Isolate the water if necessary: Use the property’s main shut-off valve if water is escaping or damage is increasing. Follow the safe mains water isolation process and do not dismantle or tamper with the water meter or utility equipment.
- Stay clear of electrical hazards: Do not touch switches, outlets or appliances, or enter standing water near electrical equipment. Keep away and call 000 if there is immediate danger; otherwise contact a licensed electrician.
- Leave the slab intact: Do not drill, cut or break concrete, or lift flooring to find the pipe. Concealed plumbing and electrical services may be present, and opening the slab could cause injury or further damage.
Check the water meter
Turn off all taps, irrigation and water-using appliances, then record or photograph the meter reading. Do not use any water for a period, then check the reading again.
Before interpreting the result, confirm that toilets, hot-water equipment and automatic appliances have not used water. Follow the current Sydney Water instructions for your meter type.
A changed reading or continued movement indicates water is passing through the metered supply and warrants investigation. It does not prove the leak is beneath the slab or show its location. A stationary meter does not rule out an intermittent leak or a drainage leak, as wastewater does not pass through the incoming-water meter.
Arrange professional leak detection and repair
A licensed plumber can assess the pipework and narrow down the likely source before any concrete is opened. Depending on the system and site, this may involve pressure testing, acoustic equipment or thermal imaging; no single method works in every situation. Non-invasive checks used to locate pipes beneath a floor identify probable routes, but professional confirmation is needed before opening the slab.
Once the leak is located, the plumber will decide whether a local repair, a rerouted pipe or replacement of a deteriorated section is appropriate. The repaired service must be tested before the opening is reinstated. Check how underground leak repairs are priced. The final price depends on the confirmed cause, scope, access, location, materials, labour, current market conditions and any further faults found.
For a suspected slab leak, contact our licensed Sydney leak detection plumbers to arrange professional assessment and repair advice.