The visible burst-pipe-through-the-ceiling scenario is the easy one. The leaks that actually cost homeowners the most are the slow, hidden ones — pinhole drips behind drywall, slab leaks under concrete, weeping fittings in crawlspaces. These can run for months before you notice, racking up water bills, rotting subfloors, and feeding mould. Here are the 8 specific signals that mean you almost certainly have a hidden leak somewhere, ranked by how often we find each one on Lower Mainland leak-detection calls.
1. Your water bill jumped without an obvious cause
This is the single most common reason for a leak-detection call. Compare your last three months of Metro Vancouver utility bills to the same three months last year. A jump of 20% or more, with no new occupants or new appliances, almost always indicates a leak. Do the 30-minute meter test (we covered it in detail in our 'water bill spike' post) to confirm.
2. A damp spot on a wall or ceiling that doesn't dry
Drywall stains from above usually trace to a supply or drain line in the floor or wall above. The stain might be small — just a faint brownish ring or a slightly darker patch. Touch it: if it's cool, water is still active behind it. If it's room-temperature dry, the leak may have stopped (but the damage continues). Either way, opening the wall now is cheaper than waiting for mould to develop.
3. Mould smell with no visible mould
Mould grows where it's consistently damp. In Lower Mainland's already-humid climate, a hidden leak adds the missing ingredient — sustained moisture. A musty smell in a specific room or a specific closet that doesn't go away with ventilation usually means water is somewhere in that area's walls or under the floor.
4. A hissing sound near the meter or behind a wall
Pressurized water escaping a small opening makes a faint hiss. Press your ear to a wall in a quiet room. If you hear something between a hiss and a whisper, you have a pinhole. Acoustic leak-detection equipment amplifies this exact sound to pinpoint the leak to within inches.
5. Low water pressure house-wide
If pressure dropped at every faucet at once, the issue is between the city meter and your house. The cause could be a service-line leak, a clogged pressure regulator, or a partially-failed check valve. We diagnose with a pressure-decay test on the service line — fast, definitive.
6. Warm spots on the floor
A slab leak on a hot-water line warms the concrete above it. If your basement floor or main-floor concrete has a patch that's noticeably warmer than the rest, the supply line under it is leaking. We confirm with a thermal imaging camera, then locate the exact run.
7. Cracks in foundation or driveway, soft soil near the house
A long-running service-line leak under your front yard saturates the soil, eventually causing settlement. If you've noticed soft patches in the lawn that don't dry, new cracks in a concrete driveway, or a sinkhole forming near the line, the cause is usually a buried supply or drain leak.
8. Sound of running water when no fixture is on
Shut every fixture off, stand in the middle of the house, and listen. If you can hear water moving — a faint trickle, a steady rush, anything — there's an active leak somewhere. The location of the sound usually tells you which floor and which side of the house to investigate.
What to do if you spot any of these
Don't panic. Don't open walls speculatively. Don't pour drying agents into the affected area. Do:
- Note the location and what you observed (where, when, how it feels)
- Check the water meter (the 30-minute test above) to confirm a leak is active
- Photograph the affected area for insurance documentation
- Call a leak-detection plumber — non-destructive locating saves drywall, time, and money compared to exploratory opening
How leak detection actually works
Modern leak detection has three primary tools used in combination:
Pressure-decay testing
We isolate sections of the plumbing system, pressurize them, and watch for pressure loss. This confirms whether a leak exists and which branch it's on — within minutes.
Acoustic locating
A sensitive microphone on a probe amplifies the sound of water escaping a pipe. We walk the suspected area, listening through headphones. The signal peaks at the leak location.
Thermal imaging
An infrared camera shows temperature differences across walls, floors, and ceilings. Hot-water leaks appear as warm patches; cold-water leaks as slightly cooler ones. Works particularly well for slab leaks.
Combined, these three tools locate leaks to within inches before we open anything — saving drywall and the time it takes to patch it.
Frequently asked
How much does leak detection cost?
We bill leak-detection diagnostic time at a transparent hourly rate, quoted up front. Most residential calls take 1–2 hours from arrival to a marked location. The cost is recovered many times over in saved drywall and faster, smaller repairs.
Will my insurance cover the repair?
Most BC homeowner policies cover sudden water damage (e.g. a burst pipe that floods a room). They generally don't cover slow ongoing leaks that 'should have been caught earlier'. Our locator report and itemized invoice provide the documentation insurers ask for if you do submit a claim.
Can a leak fix itself?
Almost never. Mineral deposits sometimes temporarily plug a pinhole in copper, masking the leak for a few days or weeks — but the underlying pipe is still failing and the leak returns. Treat every detected leak as a confirmed repair.
Got the problem we just described? We answer 24/7 across Surrey, Langley, Vancouver, Burnaby, Coquitlam, Delta, White Rock, and Richmond. Call Mr. Plunger Plumbing & Drainage at (604) 870-1442 — real plumber on the line, exact ETA before dispatch, up-front quote before any work starts.