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How to keep pipes from freezing (and what to do if they freeze)

By Roof & Router Team. Updated October 11, 2026.

At what temperature do pipes freeze?

Water freezes at 32°F, but a pipe inside your house does not freeze the moment it is 32°F outside. The walls, insulation and your heating system slow the cold down. The commonly cited danger point for pipes in unheated or poorly insulated parts of a home is about 20°F outside, especially when the cold lasts several hours or the wind is strong.

Outdoor pipes and hose bibs are at risk sooner. Protect them before the first hard freeze, when it drops to 28°F or lower for a few hours.

Why frozen pipes burst

Water expands by about 9% when it turns to ice. You might expect the pipe to split right where the ice is, but that is usually not where it breaks. The ice plug traps the water between itself and a closed faucet. As more ice forms, the pressure in that trapped water climbs until the pipe gives way, often in a section where no ice has formed at all.

This is why a dripping faucet helps. It gives that trapped water somewhere to go, so the pressure cannot build. Moving water is also slower to freeze.

Which pipes are most at risk

• Outdoor hose bibs, swimming pool supply lines and sprinkler lines
• Pipes in unheated spaces: crawl spaces, basements, attics and garages
• Pipes under kitchen and bathroom sinks on outside walls
• Pipes running through exterior walls with little or no insulation
• The spot where the water line enters the house through the foundation

Before winter: one-time fixes

1. Drain and disconnect garden hoses. Close the indoor shutoff valve that feeds each outdoor faucet, then open the outdoor faucet so any remaining water can drain and has room to expand.
2. Drain sprinkler and pool supply lines following the manufacturer’s or installer’s directions. Do not add antifreeze unless the directions call for it. It is harmful to people, pets and plants.
3. Insulate exposed pipes in the garage, crawl space, attic and under sinks with foam pipe sleeves. They are cheap and slip on.
4. Add heat cable to the worst spots. For pipes that freeze every year, use UL-listed heat tape or self-regulating heat cable and follow its instructions exactly. Plug it into a GFCI outlet, never overlap or wrap the cable over itself, cover it with insulation only if the maker allows it, and replace old cable. Worn heat tape is a known fire risk.
5. Close or cover crawl space vents for the winter if your home has them, and make sure crawl space doors shut tightly.
6. Seal air leaks near pipes, such as gaps where pipes or cables pass through outside walls and around sill plates in the basement or crawl space.
7. Find your main water shutoff valve and make sure it turns. If a pipe bursts, you will need it fast.

How to keep pipes from freezing tonight

• Keep the thermostat steady, day and night. Skip the usual nighttime setback during extreme cold. A higher heating bill costs far less than a burst pipe.
• Let cold water drip from faucets served by exposed pipes. A slow, steady drip is enough. If a faucet has separate hot and cold pipes that both run along an outside wall, drip both.
• Open kitchen and bathroom cabinet doors under sinks on outside walls so warm room air reaches the pipes. Move cleaners and chemicals out of children’s reach.
• Keep the garage door closed if water lines run through the garage.
• Do not set the thermostat below 55°F, even when nobody is home.

How to tell if a pipe is frozen

The most common sign is a faucet that gives only a trickle, or nothing, when you turn it on in cold weather. You may also see frost on an exposed pipe or a bulge in it. Check the other faucets in the house too. If one pipe has frozen, others may be close.

How to thaw a frozen pipe safely

Before you start, know where your main shutoff valve is. Thawing can reveal a crack that ice was plugging, and water may start leaking as soon as it melts.

1. Open the faucet the pipe feeds. As the ice melts, flowing water helps melt the rest and relieves pressure.
2. Start near the faucet and work back toward the frozen section, so melted water can drain out.
3. Use gentle heat: an electric hair dryer, an electric heating pad wrapped around the pipe, a portable space heater, or towels soaked in hot water. Never use electrical devices while standing in water or on a wet floor, and plug them into a GFCI outlet if you can. Keep a space heater 3 feet from anything that can burn, plug it straight into a wall outlet, and do not leave it unattended.
4. Keep going until full water pressure returns.

Never use an open flame. No blowtorch, propane or kerosene heater, or charcoal stove. They can start a fire, and a torch can heat the pipe enough to burst it or damage the joints.

If you cannot find the frozen section, cannot reach it, or cannot thaw it, call a licensed plumber.

What to do if a pipe bursts

1. Check for electrical danger first. If water is near outlets, appliances or the electrical panel, or you would have to stand in water to reach the shutoff valve, do not go in. Call your electric utility or an electrician.
2. Shut off the main water valve right away. It is usually where the water line enters the house, often in the basement, crawl space, garage or near the water heater. If you have a tank water heater, turn off its gas or power too, so it does not heat while the supply is off.
3. Open faucets to drain the remaining water from the pipes.
4. Call a licensed plumber.
5. Photograph the damage before cleaning up, and call your insurance company. The Insurance Information Institute puts the average homeowners claim for water damage and freezing at about $15,400 (2019 to 2023).
6. Dry everything quickly. Mold can start growing on wet materials within a day or two, so remove standing water and run fans and a dehumidifier.

Going away in winter

Leave the heat on and set it no lower than 55°F. For a long trip, you can also shut off the main water valve and open the faucets to drain the lines, so there is little water left to freeze. If you have a well, a boiler or other systems that depend on water, ask a plumber before shutting off the main. Having someone check the house during a hard freeze helps catch problems early.

Quick answers

How long does it take for pipes to freeze? There is no fixed time. It depends on how cold it is, the wind, and how exposed the pipe is. An uninsulated pipe in an unheated crawl space or exterior wall can freeze within a few hours of hard cold, while pipes in heated rooms rarely freeze at all.

Will pipes freeze at 25 degrees? Pipes in heated parts of the house are unlikely to. Outdoor faucets, pipes in unheated garages and crawl spaces, and pipes in drafty exterior walls can, especially if it stays that cold overnight. Take the cold-snap steps whenever lows fall into the 20s.

Will frozen pipes thaw on their own? Usually, once the weather warms, but waiting raises the chance of a burst. Thaw them as soon as you notice.

What if the frozen pipe is inside a wall? Turn up the heat in the house, open nearby cabinet doors, and aim a space heater or hair dryer at the wall from a safe distance. If that does not work, a plumber may need to open the wall.

What about mobile homes? Pipes run under the floor, so check that the skirting is intact with no gaps and that the underbelly insulation is not torn. Many mobile homes rely on heat tape on the main water line, so test it before winter.

Should I drip all faucets? No. Drip only the faucets fed by pipes on outside walls or in unheated spaces.

Hot or cold water? Cold is the usual advice, because that is the line most often exposed. If a faucet’s hot line also runs along an outside wall, drip both.

Do PEX pipes freeze? Yes. PEX can stretch a little and is less likely to split than copper or rigid plastic, but it can still freeze, and the fittings can still fail. Protect it the same way.

Will homeowners insurance cover a burst pipe? Sudden bursts are often covered, but damage from neglect, such as leaving a home unheated, may not be. Check your policy.