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Leak and Freeze

Water freezes at 32°F. Every alert on this site fires at 40°F, while there is still time to act.

Leak and Freeze

How pipes freeze, and how to keep them from it

Pipes in unheated spaces generally begin to freeze when it is 20°F outside. Which pipes go first, and the winter routine that keeps them flowing.

Water freezes at 32 degrees, but a pipe inside a heated house rarely gets that cold. The ones that freeze run where the heat does not reach: outside walls, crawlspaces, garages and attics. IBHS, as cited by the International Code Council, puts the point where unprotected pipes generally begin to freeze at 20°F outside. On the coldest nights the Red Cross says to let cold water drip from faucets served by exposed pipes and to open the cabinet doors under sinks, and to keep the heat at no lower than 55°F when you leave.

Which pipes go first

IBHS says exposed and uninsulated pipes are the first part of a home to see temperatures colder than the plumbing was designed for. That means pipes in an outside wall, a crawlspace, an unheated garage or an attic. These are the spots where a temperature sensor earns its place: set it to alert at 40 degrees, which is this site's choice and leaves time to act before the water reaches 32.

On a cold night

  1. Let cold water drip from the faucets served by exposed pipes. Moving water is slower to freeze.
  2. Open the kitchen and bathroom cabinet doors so the house's warm air reaches the pipes.
  3. Keep the garage door closed if water lines run through the garage.
  4. Keep the thermostat at the same temperature day and night.

When you leave in winter

Leave the heat on, set no lower than 55°F, which is the Red Cross figure and the one IBHS repeats. If you will be gone more than a week with freezing weather ahead, IBHS suggests closing the main water valve slowly and letting a couple of faucets on the lowest floor drain. Your policy may require one or the other while the house is empty; the insurance guide says why.

Sources

  1. ICC: Build it to code to minimize damage from frozen water pipes International Code Council, accessed October 25, 2026
  2. IBHS: State of the Risk, Interior Water Damage (white paper, December 2024) Insurance Institute for Business and Home Safety, accessed October 25, 2026
  3. IBHS: Winter weather ready guide (news release, November 2024) Insurance Institute for Business and Home Safety, accessed October 25, 2026
  4. American Red Cross: Preventing and thawing frozen pipes American Red Cross, accessed October 25, 2026
  5. NAIC: Will my homeowners insurance policy cover water damage from a burst pipe? National Association of Insurance Commissioners, accessed October 25, 2026

Drafted with a language model on October 25, 2026 from the sources listed above, each opened that day. Every threshold and count on the page comes from the site's own code, held by a test. The editor samples pages after they publish; nothing here is an inspection of your house or advice from a licensed plumber or insurer.

Found an error? See Corrections.

How pipes freeze, and how to keep them from it | Leak and Freeze