A slab leak is the one plumbing job where paying for the diagnosis first genuinely saves you money on the repair. Break into a concrete floor in the wrong place and you pay to patch that hole, then pay to break in again. Here is how the two stages work, what each costs, and the signs that tell you the leak is under the slab in the first place.
Slab leak pricing: two stages, quoted separately
| Stage | Price | What it covers |
|---|---|---|
| Stage 1: non-invasive leak detection | $200 to $500+ | Acoustic listening, thermal imaging or tracer gas to pinpoint the leak without opening anything. The fee finds the leak; the repair is quoted separately |
| Stage 2: burst pipe under a slab | $1,500 to $4,000+ | Breaking into the slab at the marked spot, repairing the pipe, and reinstating the concrete and floor finish. Complex slab jobs can exceed $4,000 |
| Alternative: re-route above ground | Quoted on inspection | A new line run through the wall or roof space, with the slab line abandoned. Sometimes cheaper than chasing the leak through the concrete |
We never add these into one headline number, because you may not need the second stage at all. Detection sometimes finds the leak somewhere easier than the slab, and sometimes the honest recommendation after detection is a re-route rather than a break-in.
Signs of a leak under the slab
Most slab leaks on the Gold Coast are on the hot water line, because hot copper pipe cast into a slab corrodes from the inside over decades and eventually pinholes. That is why the first sign is often felt through your feet.
- A warm patch on a tiled or concrete floor, with no underfloor heating to explain it
- The water meter still turning with every tap, toilet and appliance in the house switched off
- A water bill that has climbed with no change in how the household uses water
- Damp or swollen skirting boards, or a musty smell in a room with no obvious water source
- The sound of running water inside the house when nothing is on
- Tiles lifting or cracking along a line, or a patch of flooring that has gone soft
- The hot water system running more than it used to, or hot water taking longer to arrive
- Outside the house, a permanently damp or unusually green patch of lawn along the wall
None of these on its own proves a slab leak. The meter test is the one to do first: turn everything off, note the meter reading, wait, and read it again. If it has moved, water is going somewhere. Our page on reading your water meter to check for a leak walks through it. Then shut the isolation valve on the hot water system and repeat. If the meter stops moving with the hot water isolated, the leak is on the hot side, which narrows the search before we even arrive.
Stage one: finding it without breaking anything
The point of non-invasive detection is to open the slab in one place, not several. A leak under concrete does not show itself where the water surfaces; water travels along the underside of the slab and along pipe runs, so the damp patch and the leak can be metres apart. Guessing from the damp patch is how floors end up with two or three patched holes.
Acoustic gear listens through the slab for the sound of water escaping under pressure and gets louder as the sensor moves over the leak. Thermal imaging picks up the warmth of a hot water leak spreading through the concrete, which is why hot side leaks are often the quickest to find. Tracer gas is for the stubborn ones: the line is drained, a harmless gas is introduced under pressure, and a detector picks it up where it escapes through the slab. Together they put an X on the floor, and the fee for that is $200 to $500+ depending on how much of the house has to be surveyed and how hard the leak is to hear.
Stage two: the repair, and what pushes it past $4,000
The $1,500 to $4,000+ range covers three things: breaking into the slab at the marked point, repairing or replacing the failed section of pipe, and reinstating the concrete and the floor finish over it. Where a job sits in that range, or beyond it, depends on:
- What is on top of the slab. Bare concrete in a garage is the cheapest to open and close. Porcelain tiles that have to be matched, or polished concrete, cost more to reinstate than the plumbing underneath them
- How deep the pipe sits and how thick the slab is
- Whether the leak is under a wall, a kitchen bench or a built-in cupboard that has to come out and go back
- Whether it is one pinhole or a section of pipe that is corroded along its length, in which case one repair leads to the next
- The pipe material. Old copper in a slab is usually repairable in one spot; old galvanised pipe often is not worth repairing at all
When several of those stack up, a slab job exceeds $4,000, and we will say so at the quote rather than partway through the floor.
When re-routing above ground is the smarter fix
Sometimes the best answer to a slab leak is to leave the slab alone. If the pipe is old copper that has pinholed once, it will likely pinhole again somewhere else along the same run. Rather than break in, repair, and wait for the next warm patch, we can run a new line through the wall cavity or roof space to the same fixtures and abandon the section in the slab entirely. There is no concrete to cut and nothing to reinstate, and the new pipe is somewhere it can be reached in future.
Re-routing is quoted on inspection because it depends on the distance and the route, but it is often cheaper than chasing the leak through the slab, particularly on a long hot water run or a tiled floor. Jieye will tell you which option is cheaper for your house once detection has shown where the leak is and what the pipe looks like. We do not have a preference; we have whichever one costs you less and holds up longer.
Insurance and the water bill
Home insurance commonly covers the damage a hidden leak causes and the cost of finding and getting to it, while excluding the worn pipe itself. Policies differ, so check yours and keep the detection report, the photos and the invoices together. Separately, Gold Coast water customers can apply for a concealed leak remission on the excess water once a licensed plumber has repaired the leak. Our page on concealed leak water bill remission explains what the application needs, and our invoice carries the licence number it asks for.
Warm patch on the floor or a meter that will not stop? Call Hills Plumbing & Gas on 0472 657 042 or book through our Leak Detection service page. We find it first, then quote the fix, and we tell you if a re-route is the cheaper way out.