How to Prevent Frozen Pipes in a Calgary Winter

Short answer: Keep the house at 15°C or warmer, disconnect hoses and shut off outdoor taps, insulate pipes in garages, crawlspaces and outside walls, and open cabinet doors under sinks on the coldest nights. If a pipe has already frozen, shut off the main water valve first, then thaw it gently. Never use an open flame.

Frozen pipes are one of the most preventable emergencies in a Calgary winter, and the fixes are mostly cheap and boring. The pipes at risk are the ones in unheated or exterior-wall spaces, and a cold snap after a mild spell is when most of them let go.

Which pipes are most at risk?

Where	Why it freezes	What to do
Outdoor taps (hose bibs)	A hose left on traps water in the valve	Disconnect the hose and shut off the inside valve. See our outdoor tap guide
Garage and crawlspace lines	Unheated space	Insulate the pipe, seal drafts, keep the garage door closed
Sinks on outside walls	Cold wall, closed cabinet	Open the cabinet doors on cold nights
Pipes near the rim joist in the basement	Drafts where the house meets the foundation	Insulate and seal the gap
The water service line and meter	Frost driven deep in a long cold spell	Keep the meter area warm. The City may ask at-risk homes to run a trickle of water

Before the cold snap

• Disconnect and drain outdoor hoses, and shut off outdoor taps at their inside valve.
• Insulate exposed pipes in the garage, crawlspace and along exterior walls. Foam pipe sleeves from the hardware store are cheap and quick.
• Seal drafts around pipes where they pass through outside walls and the rim joist.
• Keep the house above about 15°C, even when you are away. Our furnace checklist helps keep the heat on.
• Know where the main shut-off is and make sure it turns. It is usually where the water line enters the basement, near the meter.

On the coldest nights

• Open cabinet doors under sinks on outside walls so warm air reaches the pipes.
• Let a tap on a vulnerable line run at a thin trickle. Moving water is much harder to freeze.
• Do not turn the thermostat way down overnight during a deep cold snap.

How do you know a pipe is frozen?

The City of Calgary lists the signs on its frozen water lines page: little or no water coming out of the taps, frost on pipes inside the house, or flooding from a pipe that has already burst.

A pipe has frozen: the first ten minutes

1. Shut off the main water valve. A frozen pipe often has a split you cannot see yet, and it floods the moment it thaws.
2. Open the nearest tap to relieve pressure and let water out as the ice melts.
3. Warm the area gently with a hair dryer or a space heater kept well back from anything that can burn. Never use an open flame or a torch.
4. Call if you cannot find the frozen section, if it has already burst, or if no water is reaching the house at all.

If the whole house has no water and the main shut-off area is frosty, the service line itself may be frozen. The City asks homeowners to contact 311 when water is still not flowing. The homeowner is responsible for the part of the service on their side of the property line, including the meter. If water is already on the floor, our burst pipe guide walks through what to do next.

Safe to do yourself, and when to call

Safe to do yourself: insulating exposed pipes, disconnecting hoses, opening cabinets, running a trickle, and thawing a short exposed section with a hair dryer after the main is off.

Call a licensed plumber: if a pipe has split or is leaking, if the frozen section is inside a wall or ceiling, if the same pipe keeps freezing, or if you want a frost-free outdoor tap or pipe rerouted away from an outside wall.

Common questions

What temperature do pipes freeze at?

Water freezes at 0°C, but pipes inside a heated house usually freeze only when the space around them gets that cold, which happens in garages, crawlspaces and outside walls during a long cold snap.

Should I drip my taps in a Calgary cold snap?

On a tap fed by a pipe that has frozen before, or that runs along an outside wall, a thin trickle on the coldest nights is cheap insurance.

Can I use a torch to thaw a frozen pipe?

No. An open flame can start a fire inside the wall and can damage the pipe. Use gentle heat and shut off the water first.

Does Poly-B pipe freeze?

Any water pipe can freeze. Older Poly-B is also more likely to crack when it does. Here is how to tell if you have it.

Related guides

• How to winterize your outdoor faucets in Calgary
• What to do when a pipe bursts