Slab leaks — leaks in the water or sewer lines that run under your concrete slab — are one of the few plumbing problems that get dramatically more expensive the longer you wait. A pinhole leak in a copper line under a slab in Flinders, Shell Cove or Albion Park can quietly soak the sub-floor for months before you see a single damp patch in the carpet.
Early warning signs of a slab leak
- Your water meter keeps ticking over with every tap in the house turned off
- Unexplained jump in your Sydney Water bill (often double or triple the usual)
- A patch of floor that feels warm under bare feet (hot water line leak)
- Damp, musty smell in one room — especially carpet-on-slab bedrooms
- Hairline cracks in tile grout or skirting that weren't there last year
- Hot water unit running constantly because the line is venting underground
Why slab leaks happen on Illawarra houses
Most slab leaks we see are on copper water lines installed pre-2000 that have either suffered electrolysis from poor earthing or have rubbed against the slab itself at penetration points. Sewer slab leaks are usually broken joints from minor ground movement or, in older Wollongong and Port Kembla homes, corroded cast-iron.
How we find a slab leak without jackhammering your floor
Leak detection has come a long way. On a typical call we'll combine three techniques to pinpoint a leak to within 200mm before any concrete is touched:
- Pressure test — isolate the line and watch pressure drop to confirm and grade the leak
- Acoustic listening — surface microphones over the slab pick up the hiss of a pressurised leak
- Thermal imaging — handheld FLIR camera shows hot-water-line leaks as a clear warm trace
- Tracer gas (for stubborn cases) — a safe inert gas is pushed through the line and sniffed out at the surface
Once we've marked the spot, we'll walk you through your repair options. For a single isolated leak we usually saw-cut a small section, repair, and reinstate. For older homes with multiple suspect joints, re-routing the line through the wall cavity or ceiling is often cheaper than chasing leak after leak.
Don't ignore it
A burst pipe inside the house gets dealt with in an hour. A slab leak gets dealt with in floors, carpets, kitchens and insurance claims. If your water bill has spiked and you can't explain it, get a leak detection booked — the inspection itself is quick, and it's a tiny fraction of what an unchecked slab leak will cost you.
Frequently asked questions
- How do I know if I have a slab leak versus a leaking tap?
- Turn every tap, washing machine and dishwasher off in the house, then check your water meter dial. If it's still spinning after 15 minutes, water is escaping somewhere downstream — and if you can't see it anywhere visible, the slab is the prime suspect.
- Will my home insurance cover a slab leak?
- Most policies cover the resulting water damage (carpets, cabinetry, floors) but not the cost of finding and fixing the leak itself. Either way, document everything with photos from the moment you suspect a leak and call your insurer before you start any repair.
- Do I really need leak detection equipment, or can you just dig?
- Modern detection is much cheaper than exploratory digging. A 1-hour detection call narrows the leak to within 200mm. Digging blind through a tiled or polished concrete floor in Flinders, Shell Cove or Shellharbour without that confidence is a very expensive guess.
- Can a slab leak be relined instead of dug up?
- If the leak is on a sewer or stormwater line, yes — pipe relining is often the cleanest fix and avoids cutting the slab entirely. Pressurised water lines can't currently be relined and need to be repaired or re-routed.
- How urgent is a suspected slab leak?
- Treat it as urgent but not emergency — book within a week. Unlike a burst pipe, you're not flooding right now, but every day of leaking under a slab is more damage to sub-floor, more wasted water, and a higher Sydney Water bill.