Frozen pipes — how to prevent them, and how to thaw them without a flood

Water expands when it freezes. In a pipe, that builds pressure between the ice and a closed faucet until something gives — often a split that doesn't start spraying until the ice melts. A single burst pipe can release hundreds of gallons, so a few minutes of prevention on the coldest nights is worth it.

Which pipes freeze

The ones exposed to cold air: pipes in exterior walls, unheated garages, crawl spaces, basements, and attics, under kitchen and bathroom sinks on outside walls, and outdoor hose bibs and sprinkler lines.

Before a hard freeze

• Disconnect garden hoses and shut off and drain outdoor faucets, if you have an indoor shutoff valve for them
• Insulate exposed pipes in unheated areas with foam pipe sleeves — cheap and easy
• Seal drafts near pipes (gaps where pipes enter the house, around vents)
• Know where your main water shutoff is — see find every water shutoff in your home

On the coldest nights

• Let faucets on outside walls drip — both hot and cold for single-handle faucets. Moving water is harder to freeze, and an open faucet relieves pressure if ice does form
• Open cabinet doors under sinks so the room's warm air reaches the pipes
• Keep the thermostat steady, day and night — don't turn it way down to save money on a bitter night
• Going away? Leave the heat on. The Red Cross says no lower than 55°F; insurance industry guidance says 65°F, because the inside of an exterior wall runs colder than the room. In a deep freeze, lean toward the warmer number
• Keep the garage door closed if there are water lines in the garage

If a pipe is frozen

Signs: you turn on a faucet and get only a trickle or nothing, or you see frost on a pipe.

1. Open the faucet the pipe feeds. As ice melts, flowing water helps melt the rest, and it relieves pressure
2. Apply gentle heat to the frozen section, starting closest to the faucet and working back: a hair dryer, a heating pad, a space heater kept a safe distance away (never left unattended), or towels soaked in hot water
3. Keep going until full water pressure returns, then check other faucets — if one pipe froze, others may have too

Never use a torch, propane heater, charcoal, or any open flame — it's a fire risk, and overheating a pipe can make it burst. If you can't find or reach the frozen spot, or it won't thaw, call a plumber.

If a pipe bursts

1. Shut off the main water valve immediately
2. Turn off electricity to the affected area if water is near outlets, appliances, or the panel — only if you can do it safely
3. Photograph the damage before cleanup, for insurance
4. Call a plumber, then your insurer (or your landlord, if you rent — it's generally their repair)
5. Start drying things out quickly — mold can start growing within a day or two

Quick reference

• Drip faucets on outside walls; open sink cabinets on cold nights
• Away from home? Leave the heat on — at least 55°F, and closer to 65°F in extreme cold
• Disconnect hoses and insulate exposed pipes before winter
• Frozen: open the faucet, warm the pipe gently — hair dryer, heating pad, warm towels
• Never use an open flame
• Burst: shut the main valve first, then call a plumber