A radiant floor leak is diagnosed through pressure testing and thermal imaging before anyone breaks into a slab or subfloor to find it.
Tell us what you need—we’ll call you back fast.
Quick answer
A suspected leak in a hydronic radiant floor loop is diagnosed by first confirming the system is actually losing pressure over time, then narrowing down which loop is affected at the manifold, and using tools like thermal imaging or moisture detection to pinpoint the location before any flooring or slab is opened. This staged approach avoids unnecessary demolition, since a real leak location can often be narrowed to a small area without guessing.
Need a licensed gas fitter for your hot water / boiler? Call CANRO at (604) 359-1081 — residential natural-gas heating and hot water across Metro Vancouver since 1999.
Not every pressure drop on a boiler system means a leak in the radiant tubing itself; a failing expansion tank, a slowly weeping valve or fitting elsewhere in the mechanical room, or even normal minor pressure fluctuation with temperature can look similar at first glance. The first diagnostic step is confirming the pressure loss is real and ongoing, then checking that it isn't coming from an easily visible source, like a fitting in the mechanical room, before assuming the buried or embedded tubing itself is compromised.
A homeowner can safely observe and report the boiler's pressure gauge reading over a few days, and note any damp spots, unexplained musty smell, or warm patches on a floor that shouldn't be warm, all useful clues before a technician arrives.
If the system has multiple radiant loops off a manifold, isolating each loop one at a time and monitoring pressure can identify which specific loop is losing water, narrowing a whole-house problem down to one room or area. This step alone often saves significant time compared with searching an entire slab or subfloor.
Loops that are rarely used, or that were part of more recent work such as a bathroom addition, are statistically more likely leak points than long-established loops that have been trouble-free for years, though that's a starting point for investigation, not a conclusion on its own.
Once a loop is narrowed down, thermal imaging can sometimes reveal a warm, damp patch on a slab or floor surface where leaking water is locally warming the area compared with the surrounding floor, though this works best when the leak is active and the system is running. Moisture meters can help confirm dampness in a suspected area, particularly useful when a slab leak is showing up as a damp spot on a floor above or a musty smell in a basement below.
These non-invasive tools don't always pinpoint a leak with certainty on the first pass, especially with a small, slow leak, and sometimes repeated observation over a heating cycle or two is needed to build enough evidence before committing to opening a floor.
| Situation | Typical Next Step |
|---|---|
| Leak location narrowed with reasonable confidence | Targeted opening of a small section rather than the whole floor |
| Leak suspected but not confidently located | Further monitoring or additional diagnostic passes before opening anything |
| Leak in an accessible staple-up run | Often reachable from below without disturbing the finished floor above |
| Leak in embedded in-slab tubing | Usually the more disruptive scenario, sometimes leading to a discussion of loop abandonment vs. repair |
In some in-slab cases, rather than cutting into a finished slab, the affected loop is capped off and abandoned while a new loop is run through a different path, which can be less disruptive overall than chasing an exact pinpoint repair inside existing concrete.
Once a leak is repaired, the loop and the wider system should be pressure-tested again before the floor is closed back up, since discovering a second, related issue after everything is sealed up is far more costly than catching it at the same time. Ongoing small pressure losses after a repair are worth investigating immediately rather than waiting to see if they get worse.
Radiant and radiator loops share water (and often pressure) with a natural-gas boiler, so changes to the boiler's fill pressure, relief valve, or combustion venting are not homeowner work. That belongs to a Technical Safety BC licensed gas fitter. CANRO holds gas licence LGA0043870 and boiler licence LBP0046450. If you ever smell gas near the mechanical room, leave the house first and call FortisBC's emergency line, 1-800-663-9911, from outside.
Safety note
Radiant and radiator loops share water (and often pressure) with a natural-gas boiler, so changes to the boiler's fill pressure, relief valve, or combustion venting are not homeowner work. That belongs to a Technical Safety BC licensed gas fitter. CANRO holds gas licence LGA0043870 and boiler licence LBP0046450. If you ever smell gas near the mechanical room, leave the house first and call FortisBC's emergency line, 1-800-663-9911, from outside.
The clearest early sign is your boiler's system pressure gradually dropping over days without an obvious cause, sometimes along with a damp spot, musty smell, or an unexplained warm patch on the floor.
Often yes, at least to narrow down the general area, using pressure isolation by loop, thermal imaging, and moisture detection, though pinpointing an exact spot sometimes still requires a small targeted opening.
Not always; sometimes a leaking loop is capped off and a new loop rerouted instead of repairing the exact leak point, which can be less disruptive than opening a finished slab.
Pressure loss can come from several sources besides visible leaking, including a failing expansion tank or a slow weep at a fitting, so a technician typically rules out the easily visible causes before assuming the embedded tubing itself is the source.
A slow leak generally isn't an immediate emergency, but ongoing pressure loss should be looked at promptly rather than left indefinitely, since low system pressure can eventually cause other operational issues.
Family-run, TSBC-licensed (gas LGA0043870 · boiler LBP0046450), serving Metro Vancouver homes since 1999. Residential, natural gas only.
Call (604) 359-1081 Email info@canroheat.ca“Canro does an amazing job! Super professional and skilled with everything—boilers, furnaces, and AC. Always a pleasure working with them!”
“Five stars for Canro. We needed a replacement of a 30-year-old boiler. A new high-efficiency unit was installed—clean, professional work.”
“I can’t speak highly enough about George, who was recommended for a boiler service call for my parents’ home. George is excellent.”
25+ years keeping Metro Vancouver homes comfortable. Honest advice, upfront pricing, work that lasts.