Long-form guide · 12-minute read
Slab leak detection. Located within inches. Concrete stays intact.
Slab leaks are water leaks inside the plumbing lines beneath a concrete floor. Left undetected, they cause foundation damage, mold, and silent water bills running into the thousands. We locate them with non-invasive thermal, acoustic, and ground-penetrating radar — typically within a 5–10 cm window — before any concrete is touched.
What is slab leak detection?
A slab leak is a water leak in the copper or PEX plumbing lines embedded in — or running beneath — a concrete floor slab. Most homes built before 2000 used soft copper buried directly in the slab during pour, and over 15–25 years that copper develops pinhole leaks from soil acidity, electrolysis with rebar, or mechanical wear from slab settlement.
Slab leaks are particularly costly because the leak itself is invisible. Water travels through the soil and concrete before it surfaces — by which time the slab is saturated, the framing is wet, and mold may already be forming. The earlier a slab leak is located, the smaller the repair.
Modern non-invasive detection combines three technologies: thermal imaging to see the heat signature of a hot-water leak through the slab, acoustic correlation to triangulate the sound of pressurised water escaping, and ground-penetrating radar to confirm the pipe location relative to rebar before any concrete is cut.
When you need slab leak detection
If you're seeing any of these signs, professional detection is warranted:
- Unexplained warm spots on a tile, vinyl, or hardwood floor
- Cracks appearing in foundation walls or floor slab
- Sound of running water with every fixture confirmed off
- Mold or mildew patches at the floor-wall edge
- Water bill suddenly doubles or quietly climbs over months
- Lower water pressure than usual at one or more fixtures
- Standing water in landscaping next to the slab
- Floor tile or vinyl that lifts, bubbles, or stains in a single spot
Why early detection saves you $20,000+
A small slab leak detected and repaired in week one is typically a single $250–$500 repair patch. The same leak ignored for 6 months saturates the slab, soaks the bottom plate of framing, breeds mold inside the wall cavity, and turns into a $15,000–$30,000 restoration project with insurance deductibles, hotel stays, and weeks of disruption.
How we detect it
- 1
Free phone consult
Call 604-239-9934. We listen to symptoms (warm spots, sound, water bill) and decide if site visit is warranted.
- 2
Map the in-slab plumbing
We start with the original blueprints if available, then verify with ground-penetrating radar (1.6 GHz) which maps every line and rebar in the slab non-invasively.
- 3
Pressurise and listen
With the system pressurised and all fixtures off, we use an acoustic correlator and ground microphone to triangulate the leak sound across the suspected slab area.
- 4
Confirm with thermal
Thermal imaging confirms the temperature differential — hot-water leaks show warmer than surrounding slab; cold-water leaks show cooler. Two technologies confirming each other = high-confidence location.
- 5
Mark and document
We mark the leak location on the slab in spray paint and produce a written report with annotated thermal imagery, GPR profile, and acoustic correlator output.
- 6
Hand off for repair
Your plumber now knows exactly where to cut a 200 mm × 200 mm patch — instead of jackhammering the whole bathroom. Repair takes hours, not days.
Detection technologies we use
Thermal Imaging (FLIR)
Sees temperature differentials caused by hot-water leaks through 100–200 mm of concrete. Best first-pass non-contact method.
Learn moreAcoustic Correlation
Triangulates the sound of pressurised water escaping. Two sensors on the supply line; arrival-time difference yields location.
Learn moreGround Penetrating Radar (1.6 GHz)
Maps the in-slab plumbing layout and rebar so the repair patch can be cut between bars without structural compromise.
Learn moreTracer Gas (5% H₂ / 95% N₂)
Hydrogen-nitrogen mix injected into the suspect line — gas escapes at the leak and is sniffed at the surface. Used when acoustic conditions are unfavourable.
Learn moreCommon scenarios
Single-family home (1985 build)
Owner noticed a warm spot near the master bedroom doorway. Thermal showed a clear heat plume; acoustic correlator narrowed to a 15 cm window. Plumber cut a single tile, repaired the hot-water line, retiled — done in one day. Total: ~$1,800.
200-unit high-rise (14th floor)
Strata had ceiling damage on the 14th floor. Source unit identified on the 15th floor: failed copper riser in the bathroom slab. GPR mapped rebar; targeted 20 cm × 20 cm patch in floor; one inter-unit insurance claim avoided.
Commercial tenant improvement
Restaurant kitchen had unexplained water at the floor drain. Slab plumbing was mapped, leak located under prep area in 90 minutes. Repair scheduled for off-hours, no business interruption.
Typical pricing
Typical range. Final price quoted on the free phone consult.
- Single-leak residential detection typically falls in this range.
- Insurance often reimburses detection costs when active water damage is present.
- Free phone consult before any site visit — we'll tell you if it's not warranted.
- Commercial/strata projects quoted by scope.
Frequently asked questions
How do you locate a slab leak without breaking the floor?
We use three non-invasive technologies in combination. Thermal imaging detects temperature differentials through concrete (especially effective for hot-water leaks). Acoustic correlation triangulates the sound of pressurised water escaping. Ground-penetrating radar maps the plumbing layout and rebar so we know exactly where the pipe runs. All three see through the slab without touching it.
How accurate is slab leak location?
Typical horizontal accuracy is within 5–10 cm. Multi-technology confirmation (acoustic + thermal + GPR all agreeing) tightens accuracy to a window your plumber can cut with a single tile-sized patch — not a whole-room jackhammering.
What are the most common signs of a slab leak?
Warm spots on the floor (hot-water leak), unexplained foundation cracks, sound of running water with everything off, sudden spike in your water bill, mold at the floor-wall edge, and lower water pressure than usual. Even one of these symptoms warrants a phone consult.
How much does slab leak detection cost in BC?
Residential slab leak detection typically runs $350–$850 CAD depending on property size and complexity. Most BC home insurance policies reimburse the detection cost when active water damage is present. Free phone consult before any visit.
Is slab leak repair covered by insurance?
The repair (cutting, plumbing work, restoration) is typically covered when sudden and accidental. The cost of detection is usually covered too. The actual pipe replacement may not be — read your policy or ask your adjuster. Our detection report is formatted for insurance review on first look.
How long does slab leak detection take on-site?
Most residential slab leak jobs take 1–2 hours on-site. The free phone consult that precedes it is about 5 minutes. The full written report is delivered by email within 24 hours.
Can a slab leak fix itself?
No. Slab leaks worsen as soil erosion enlarges the failure point, mineral deposits don't reliably seal copper pinhole leaks at supply pressure, and the longer the leak runs the more damage accumulates beneath the slab.
What's the difference between a slab leak and a foundation leak?
A slab leak is in the plumbing pipes inside or under the slab — it's an active pressurised water source. A foundation leak is groundwater intruding through cracks in the foundation walls — typically a waterproofing or drainage issue. The diagnostic and repair paths are completely different.
Will I see the leak on a normal home inspection?
Usually not. Home inspectors rarely have thermal imaging, acoustic, or GPR equipment. A standard home inspection misses most slab leaks. Pre-purchase slab leak inspection is a separate specialist service.
Can a slab leak cause foundation damage?
Yes. Soil erosion beneath the slab can cause settlement, which causes foundation cracking, uneven floors, and door/window misalignment. Hot-water leaks accelerate the damage by softening soil. This is why early detection matters.
Do you do slab leak detection in commercial buildings?
Yes — commercial slab leak detection is a major part of our work. Restaurants, retail, offices, healthcare. We work around operations to minimise business disruption — same equipment, larger scope.
Can you locate slab leaks in high-rise condos?
Yes. In high-rise stratas, we typically identify the source unit (often the floor above the visible damage), map the in-slab plumbing, and produce inter-unit subrogation evidence for the strata's insurance claim.
Related guides & services
Underground Service Line Leak Guide
Buried water main from street to house
Strata Inter-Unit Leak Guide
Locate the source unit in a multi-floor building
Hidden Water Leak Guide
Walls, ceilings, and under floors
Thermal Imaging Technology
Ground Penetrating Radar Services
Compare: Acoustic vs Thermal vs GPR
Ready to talk to an expert?
Free phone consult — no pressure, no obligation. A Leak.ca technician will tell you whether you actually need detection.