Frozen Pipe Thawing in Toronto

Where pipes freeze

• Sinks set against exterior walls, worst where closed cabinets trap the chill.
• Pipes running through garages, crawlspaces or above unheated porches.
• Lines near the sill plate, where cold air leaks in at the top of the foundation.
• Outdoor hose bibs left with the inside valve open.
• Bathrooms over garages, common in houses built in the 1980s and 1990s.

Safe thawing steps

1. Open the tap the pipe feeds so melting water can flow out.
2. Open cabinet doors to let room heat in.
3. Run a hair dryer along the pipe, beginning at the faucet end and working toward the ice.
4. A space heater with tip-over protection can warm a small room, kept well clear of anything flammable.
5. Keep heating until full flow returns, then check the pipe for drips.

Things never to use

• Never use an open flame, a propane torch or a barbecue lighter. Fires start this way every winter.
• Do not pour boiling water on a pipe. Rapid heating can crack cast iron and old fittings.
• Do not leave a heater running unattended in a closed crawlspace.

Insulation and heat tape

Foam pipe insulation sleeves are cheap and work well on exposed pipes in basements and crawlspaces. Seal gaps at the rim joist with foam or caulk. For pipes that cannot be moved, self-regulating heat cable, plugged into a GFCI outlet and installed to the maker's instructions, keeps them just above freezing. In the worst cold, leave a small drip running from the vulnerable tap overnight. The cost of a little water is far less than the cost of a burst. Our guide to preventing frozen pipes has more.