Preventing Frozen Pipes: What Works and What's Just Folklore

Pipes freeze in predictable places: unheated crawl spaces, uninsulated exterior walls, attics, and garages. A little preparation before a hard freeze prevents the vast majority of frozen-pipe damage, which is otherwise one of the most expensive common home insurance claims.

Why pipes actually burst

Ice forming inside a pipe doesn't usually burst the pipe at the ice itself. As water freezes and expands, it increases pressure in the sealed section of pipe between the ice blockage and a closed faucet downstream — that trapped, pressurized water is what ruptures the pipe, often at a point some distance from the ice itself.

Identify the vulnerable pipes in your home

• Pipes running through unheated crawl spaces or basements.
• Pipes in exterior walls, especially on the side of the house that gets the most wind.
• Supply lines to outdoor spigots and hose bibs.
• Pipes in an attic or over an unheated garage.
• Any pipe run that was added later and routed through a non-standard, less-insulated path.

Before the cold snap arrives

1. Disconnect and drain garden hoses, and shut off and drain interior valves feeding outdoor spigots if your home has them.
2. Wrap exposed pipes in unheated areas with foam pipe insulation sleeves or heat tape rated for the purpose.
3. Seal air leaks near pipe runs — gaps around dryer vents, cable entry points, and foundation penetrations let cold air reach pipes directly.
4. Know where your main water shutoff valve is before you need it in an emergency.

During an extreme cold snap

• Open cabinet doors under sinks on exterior walls so warm room air can reach the pipes.
• Let faucets served by vulnerable pipes drip slightly — moving water is much less likely to freeze than still water, and a small trickle also relieves pressure buildup if freezing starts anyway.
• Keep the thermostat set to the same temperature day and night rather than setting back overnight, and keep it set even if you're away.
• For a home that will be unoccupied through a cold spell, don't set the heat below roughly 55°F (13°C).

If you suspect a pipe is already frozen

Turn on the nearest faucet fed by that pipe so it can drip as it thaws and relieve pressure, then apply gentle heat to the suspected frozen section with a hair dryer, heating pad, or towels soaked in hot water, working from the faucet end toward the blockage. If you can't locate the frozen section, or water doesn't return after a reasonable thawing effort, call a licensed plumber before the situation escalates into a burst pipe.

If a pipe has already burst

Shut off the main water supply immediately, then the electricity to any affected area if water is near outlets or fixtures, and call a plumber. This is not a situation to wait out — even a small burst can release many gallons per minute.