Frozen and burst pipe questions, answered

Trapped water under pressure. Ice seals the pipe at its coldest point, and the water between that plug and a closed tap has nowhere to go as more of it freezes and expands about 9 per cent. The pressure climbs until the weakest spot fails, usually where there is little or no ice. See why frozen pipes burst.

No single number. Exposed or unprotected pipes can freeze on any night below about −5 °C; pipes in heated interior walls survive −40 °C. Duration, drafts and how much house heat reaches the pipe matter as much as the forecast.

Yes. Most frozen pipes in occupied homes freeze with the heat on, in exterior walls, sink cabinets on outside walls, garages and cantilevered floors where house heat does not reach.

In hours. This site's model gives about 1.8 hours for a bare ½-inch pipe in still −20 °C air, and under an hour with a draft. Foam roughly doubles those times.

Not necessarily. Copper can stretch on one freeze and split on the next, and fittings can loosen. A pipe that froze once will freeze again unless you change its conditions.

The split usually happened during the freeze, but the ice plug upstream held the water back. When the thaw melts the plug, water reaches the split and the leak begins.

Find the main shut-off and make sure it turns, then open the tap the frozen line feeds. That prepares you for a split and relieves pressure as the ice melts.

No. Never use a torch or any open flame. It can set framing and insulation on fire and create steam pockets. Use a hair dryer, warm towels, a heating pad or a warmed room instead.

Toronto says thawing can take one to six hours. If gentle heat has not brought water back within a few hours, the pipe is inside a finished wall, or you cannot find the frozen section, call a plumber.

Open. An open faucet gives meltwater an exit, relieves pressure and shows you the moment water starts moving.

A steady pencil-thin stream, not drops. As a guide, Winnipeg's post-thaw flow fills a 250 ml cup in about 15 seconds. Run it from the tap that the at-risk line feeds. See the dripping tap guide.

No. Foam slows heat loss and buys hours, but adds no heat. In a space that stays below zero for days, pair it with heat cable, flowing water or rerouting.

Yes, if it is certified for use in Canada, approved for your pipe material, installed exactly as instructed, plugged into ground-fault protection and replaced when damaged or old. Old or damaged cable is a fire risk.

A connected hose traps water in the outdoor tap. On a standard bib that water freezes at the wall; on a frost-free sillcock it stops the barrel draining and can split it inside the wall.

The frost-free sillcock probably split over winter, often because a hose was left on. Close the tap and the indoor valve or main at once, and have it replaced.

The service line or meter may be frozen, or there may be a supply outage. Check your utility's outage notices, look for frost at the meter and main valve, and call your utility or 311.

It depends on where the freeze is and local rules. Usually the municipality handles its side and the owner pays for the private side, often including the meter. Calgary and Winnipeg publish their rules; confirm with your utility.

At least your utility's floor, such as 15 °C in Calgary or 12 °C in Winnipeg, plus a closed main valve, open cabinet doors and regular checks. For a long absence, draining the plumbing is safer.

Keep the house closed up and open cabinet doors on outside walls. On city water, run a thin stream at the most exposed tap. If the heat will not return before the house nears freezing, shut off the main and drain the plumbing.

The Insurance Bureau of Canada says standard policies generally cover resulting damage when the pipes were in the heated part of the home and reasonable steps were taken to maintain heat, but freezing damage in vacant homes is typically excluded. Check your own policy.

No. PEX tubing often stretches rather than splits, but it still freezes, still stops the water, and its rigid fittings and valves can crack. Keeping the pipe warm matters more than the material.

Yes, less often. Drains freeze where water sits or trickles slowly in the cold, such as a trap in an unheated space or a shallow line under a cleared driveway. The sewer side is covered by the HAUSE sewer network.

Many steps are free. Foam sleeves run about $2 to $6 per metre DIY, a heat cable about $300 to $900 installed, and a frost-free sillcock about $250 to $600, as CAD 2026 planning estimates. See the cost page.

Start with the where pipes freeze guide to find the cause, then request quotes for a permanent fix such as rerouting, sealing the cavity or heat cable.