Frozen pipes: thawing, repair and prevention

How to tell a pipe is frozen

• A tap gives a trickle or nothing during a cold snap, while others work
• Frost or a bulge is visible on an exposed pipe
• A toilet will not refill
• There are odd smells from a drain, because an ice blockage is stopping it venting

The usual locations are pipes in exterior walls, under kitchen and bathroom sinks on outside walls, in garages and crawlspaces, above unheated spaces, and at outdoor taps.

Before you start thawing

1. Find your main shut-off and make sure it works. If the pipe has split, you will need it the moment the ice melts.
2. Open the affected tap, hot and cold. Running water, even a trickle, helps melt the ice and relieves pressure.
3. Look for damage. A split, a bulge or a pushed-apart joint means water will come out when it thaws. Shut off the water first and have a plumber repair it.

Thawing safely

• Hair dryer. Start at the tap end and work back toward the frozen section, so that melting water has somewhere to go.
• Warm towels. Soak in hot water, wring out, wrap around the pipe and replace as they cool.
• Portable heater. Warm the room or cabinet, keeping the heater clear of anything flammable and off wet floors.
• Open cabinet doors to let room heat reach the pipes.
• Turn up the thermostat.

Never use a blowtorch, propane heater, charcoal or any open flame. They start fires inside walls and can boil water in the pipe.

If the frozen section is inside a wall or ceiling and you cannot reach it, raise the heat, open the taps and call a plumber.

If it has burst

1. Shut the main valve.
2. Open taps to drain the lines.
3. Switch off power to wet areas if the panel is reachable from a dry spot.
4. Catch and contain the water, and photograph the damage.
5. Call a plumber for the repair and a restoration company for the water.

See burst pipe: what to do.

Why a pipe that froze once will freeze again

It froze because cold air reached it. Unless that changes, the next deep cold snap repeats it. Typical reasons:

• The pipe runs through an uninsulated exterior wall or over a garage
• A gap in the wall or rim joist lets wind blow on it
• The room was left unheated
• A renovation moved plumbing into a colder position

Prevention

• Insulate vulnerable pipes with foam sleeves
• Seal air leaks near pipes, at the rim joist and around penetrations
• Keep the heat on, even when away, and warm enough for pipes in outside walls
• Open cabinet doors under sinks on exterior walls in extreme cold
• Let a tap drip on the coldest nights
• Shut off and drain outdoor taps each fall
• Have vulnerable runs rerouted to the warm side of the insulation if they freeze repeatedly
• Fit a leak detector with automatic shut-off if the home is often empty

Cottages and seasonal homes

A building left unheated over winter needs its water system drained and blown out, and traps protected, or it needs heat maintained and regular checks. A furnace failure in an empty building can freeze every line.

How a plumber repairs a split pipe

Once the pipe has thawed and the water is off, the damaged section is cut out and replaced. On copper this is a new length soldered or joined with fittings. On plastic piping it is a new section with the appropriate connectors. The plumber should also check the rest of the run, because a pipe that froze in one place was cold along its length and may be weakened elsewhere.

Ask the plumber what made that spot freeze and whether the run can be moved or protected. A repair in the same exposed position will fail again.

More: burst and frozen pipe water damage.