A frozen pipe can burst and flood a home, causing some of the most expensive water damage there is. Prevention is cheap and simple, and matters most for pipes in unheated spaces and exterior walls.
Before winter
Disconnect and drain garden hoses, shut off and drain exterior taps, and insulate pipes in unheated areas like crawl spaces, garages, and attics with foam pipe sleeves. Seal air leaks near pipes that let cold in.
During a cold snap
Let a vulnerable faucet drip slightly — moving water resists freezing. Open cabinet doors under sinks on exterior walls so warm room air reaches the pipes. Keep the house above about 13°C even when away.
If a pipe freezes
Open the faucet and gently warm the frozen section with a hair dryer or towels soaked in hot water, working from the faucet back. Never use an open flame. If a pipe has already burst, shut off the main immediately and call a plumber.