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Why Do Pipes Burst in Winter and How Cold Does It Have to Be?

Last updated October 26, 2026

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The short answer

What Causes the Burst

When water freezes, it expands by about 9 percent. That expansion pushes against the walls of the pipe, building pressure. Even a small ice blockage can create enough force to crack the pipe, often at a joint or a weak spot.

The burst usually happens after the ice thaws, not during the freeze itself. As the ice melts, the trapped water escapes through the crack. You may not notice the leak until water damage is already underway, which is why acting quickly matters.

How Cold Is Too Cold

There is no single number that predicts a burst, but sustained temperatures around 20 degrees Fahrenheit or below put pipes at risk. The longer the cold lasts, the higher the chance of freezing, especially in unheated areas like attics, garages, and crawl spaces.

Wind chill does not directly freeze pipes, but drafts can cool the air around them faster. Pipes on exterior walls or near gaps in insulation freeze more easily. In warmer climates, homes are often built without the same cold-weather protections, so even a short cold snap can cause trouble.

  • Keep garage doors closed if water lines run through the garage.
  • Open cabinet doors under sinks to let warm air reach the pipes.
  • Let a trickle of water run from faucets during extreme cold.
  • Insulate pipes in attics, garages, and crawl spaces.
  • Know where your main shutoff valve is before an emergency happens.

Signs of a Frozen Pipe

A frozen pipe often means little or no water flows when you turn on a faucet. You might also hear strange gurgling or banging sounds from the walls. Frost on the outside of a pipe is another clear sign that ice has formed inside.

If you suspect a freeze, turn off the water at the main shutoff valve first. Then warm the pipe gently with a hair dryer or space heater, starting near the faucet. Never use an open flame, as that can damage the pipe or start a fire.

Handling the Aftermath

Once a pipe bursts, water can soak floors, walls, and personal belongings quickly. Shut off the water immediately to limit the spread. Then remove standing water as soon as possible and start drying the area with fans and dehumidifiers.

For serious water damage, local water damage pros can inspect the affected areas, remove saturated materials, and dry the structure properly. They can also help identify hidden moisture that could lead to mold growth. Acting fast reduces the chance of long-term issues.

If you live in Port St. Lucie, keep your shutoff valve location written down. Acting fast can make a big difference in how much damage occurs.

  • Turn off the water at the main shutoff valve.
  • Open all faucets to drain remaining water from the system.
  • Take photos of the damage for your records.
  • Move furniture and rugs away from wet areas.
  • Call the pros if the water is deep or widespread.

Prevention for Next Winter

Preventing a burst is easier than cleaning up after one. Add foam pipe insulation to exposed pipes, especially in unheated spaces. Seal gaps around windows, doors, and where pipes enter the house to block cold drafts.

During a hard freeze, keep the thermostat set to the same temperature day and night. Letting the house get colder at night increases the risk. If you plan to be away, set the heat no lower than 55 degrees Fahrenheit and ask someone to check on the property.

Policies vary, and your insurer decides what is covered. Check your policy to understand what protection you have for water damage from frozen pipes.

Water damage does not wait

Every hour counts once water gets into floors and walls. One call starts the response.

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Frequently asked questions

At what temperature should I worry about my pipes freezing?

Worry when temperatures stay at or below 20 degrees Fahrenheit for several hours. Pipes in unheated areas or on exterior walls are at higher risk. In warmer climates, even a brief dip can cause problems, so take precautions during any hard freeze.

Can I thaw a frozen pipe myself?

Yes, if you catch it early. Turn off the main water valve, then warm the pipe with a hair dryer or space heater, starting near the faucet. Do not use a torch. If the pipe has already burst, shut off the water and call the pros.

What should I do immediately after a pipe bursts?

Shut off the main water valve right away. Then open all faucets to drain the system. Remove standing water with mops or a wet vacuum. Dry the area with fans and dehumidifiers. Call local water damage pros if the water has soaked walls or floors.

Call Now (772) 758-7923