What it usually means, the likely causes in order, what to safely try first, what a pro charges in Canada, and when to stop and call one.
This guide covers the common cases. Describe your exact problem and get a personalized diagnosis — free to start, with a DIY vs. call-a-pro verdict and a real cost estimate.
A pipe that freezes has usually picked the worst spot in the house to do it: an exterior wall, an unheated crawlspace, a garage ceiling, or a kitchen cabinet against an outside wall. The freeze itself cuts off water downstream, but the real danger is the split — water expanding as ice can crack the pipe, and the leak only announces itself when the ice thaws and water starts moving again. So a frozen pipe is two problems in sequence: thaw it gently and watchfully, then prevent the rerun, because pipes that freeze once have told you exactly where your insulation problem lives.
Act the same day. A frozen-but-intact pipe is a warning; a frozen-and-split pipe is a flood waiting for the thaw, and thaws don't schedule themselves. If water has already stopped to part of the house in a cold snap, start gentle thawing and locate your main shut-off now, while it's a drill rather than an emergency. If you find water actively leaking, shut off the main, then mop, then call.
Pipes routed through crawlspaces, garages, attics, and exterior walls sit in the coldest air in the house. The section that freezes is almost always the section closest to outside air — often where insulation was skipped, compressed, or fell away.
Cold air infiltration through a foundation crack, an unsealed sill, or a vent can freeze a pipe even in a heated house, because moving cold air chills far faster than still air. This is why one short section freezes while the rest of the run is fine.
Turning heat way down overnight or while away saves energy, but in a deep cold snap the air inside wall cavities can drop below freezing even when the living space feels safe. Homes that freeze often share this history.
Freezing is location-specific: the same weak point tends to freeze every cold snap, because nothing about the run changed. A repeat freeze is your map — that exact stretch needs insulation, sealing, or heat, not just another thaw.
| Job size | Typical estimate (CAD) |
|---|---|
| Simple fix — the straightforward version of this repair | $120–$250 |
| Major job — complex, hidden, or replacement-level work | $400–$1,200 |
Estimates only, calibrated to Greater Toronto Area trade rates and adjusted by region on this site — not a quote. Your exact price depends on the cause, parts, and access. A personalized diagnosis narrows this range using your specific symptom.
Gentle thawing, cabinet doors, dripping taps, and adding foam insulation sleeves afterwards are all homeowner work. Call a pro when you can't locate or reach the frozen section (inside a finished wall or ceiling), when the pipe has split, when the same run freezes repeatedly despite insulation (it may need rerouting or a heat cable installed properly), or when the main shut-off is seized — you want that fixed on a calm day, by someone prepared for what it feeds.
Often you can't until it thaws — the ice plugs the split it made. Signs to watch for as water returns: a drop in pressure, the sound of water where none should be, new drips, stains, or a meter that keeps turning with taps closed. That's why the thaw should always be supervised, with the main shut-off located first.
Yes — a slow drip keeps water moving through the vulnerable section, and moving water takes much longer to freeze solid; it also relieves pressure if ice does start forming. It uses some water, but it costs a fraction of one burst-pipe repair. Drip the faucet furthest along the vulnerable run, especially overnight.
Start exactly where it froze — that section has proven it's the coldest. Foam sleeves on accessible runs in crawlspaces, garages, and exterior-wall cabinets give the most protection per dollar, and sealing air leaks around the sill and foundation near those pipes matters as much as the sleeve itself, because drafts defeat insulation.
It's a sensible precaution many plumbers recommend: shutting the main and draining pressure from the lines (open a low tap after closing the main) means a freeze during your trip can't turn into days of flooding. If you do it, remember to account for anything that needs water while you're away, and turn the water heater to a low or vacation setting per its label.
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