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Guides · Seasonal

Frozen pipes: prevent them, thaw them, and what to do if one bursts

It does not get cold here often, which is the problem. Houses on the coast have hose bibs, crawl-space pipes and garage lines that would never pass on the prairies. A few nights at minus ten finds every one of them.

Andrew HendersonReviewed by Andrew Henderson, Red Seal plumber and founder of Pure Mechanical Group. Last reviewed November 2026.

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Drawing of a pipe being frozen with a clamp to isolate a section
Water expands when it freezes. The pipe does not.

If a pipe has burst

  1. Shut off the water at the main valve. It is usually where the water line enters the house: in the basement, crawl space, garage or a utility closet. Turn a lever a quarter turn, or a round handle clockwise until it stops.
  2. Open a tap on the lowest floor to drain what is left in the pipes.
  3. If water is near wiring, outlets or the panel, switch off the power to that area from a dry spot.
  4. Catch what you can, move what you can and take photos for your insurer.
  5. Call. A burst pipe is an emergency call at any hour.

Most bursts show up when the pipe thaws, not when it freezes. If a tap has stopped running in a cold snap, find your main valve now.

Before the cold snap

  • Disconnect garden hoses. A hose left on holds water in the hose bib and splits it inside the wall.
  • If your outdoor taps have an indoor shut-off, close it and open the outside tap to drain it.
  • Keep the heat on, at 15°C or more, even if you are away.
  • Open the cabinet doors under sinks on outside walls.
  • Let a cold tap on an exposed line run at a pencil-width trickle overnight.
  • Insulate pipes in crawl spaces, garages and unheated rooms. Foam sleeves are cheap and go on in minutes.
  • Going away? Have someone check the house daily. Many insurers require it in winter.

Thawing a frozen pipe

  1. Open the tap the pipe feeds, so melting water has somewhere to go.
  2. Find the frozen section. It is usually where the pipe passes through an outside wall, crawl space or garage. It may be frosted or bulged.
  3. Warm it gently, from the tap end back toward the frozen part: a hair dryer, a heating pad or towels soaked in hot water.
  4. Keep going until full flow returns, then check the whole length for leaks.

Stop and call a plumber if

  • You cannot find or reach the frozen section
  • The pipe is bulged or split
  • Water appears in a wall or ceiling as it thaws
  • No water anywhere in the house

Call 1-800-604-0631, any hour.

Never use a torch, a heat gun on plastic pipe, or any open flame. It is how houses burn down in cold snaps.

Fixing it for good

A pipe that froze once will freeze again. The lasting fixes are a frost-free hose bib (hose bib installation), a shut-off valve you can actually reach and turn (shut-off valve replacement), and moving or insulating the pipe run.

Repairs to a burst pipe are hourly: $289 for the first hour on site and $189 an hour after in regular hours (9 to 5, Monday to Friday), and double outside them. Finding a leak inside a wall is covered under leak investigation.

Questions people ask

At what temperature do pipes freeze?

Pipes in unheated spaces are at risk once it stays below about minus six for several hours. Wind makes it much worse for pipes in vented crawl spaces and outside walls.

Which pipes go first?

Hose bibs, pipes in garages and crawl spaces, and kitchen or bathroom supply lines on north-facing outside walls.

Does Poly-B freeze differently?

It can survive a freeze that would split copper, but its fittings often do not. See Poly-B and home insurance.

Water where it should not be?

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