Frozen Pipes: What to Do First, How to Thaw Them Safely, and How to Prevent a Burst

A frozen pipe does not flood anything while it is frozen. The damage comes from pressure: ice blocks the pipe, pressure builds between the ice and the closed faucet, and the pipe splits. The leak starts when the ice melts, often hours later, sometimes inside a wall. A faucet that gives only a trickle on a bitter morning is the warning, and what you do in the next hour decides whether this is a hair dryer job or an insurance claim.

This page covers how to recognize a frozen pipe, the three things to do before you apply any heat, how to thaw it safely following American Red Cross and CDC guidance, what to do if a pipe has burst, and how to keep it from happening again. It builds on the freeze section of our winter guide.

Signs of a Frozen Pipe

• Little or no water at a faucet. The Red Cross rule: if you turn on a faucet and only a trickle comes out, suspect a frozen pipe.
• Frost on the outside of an exposed pipe, or a pipe that looks bulged or cracked.
• The location fits. Pipes freeze where they run through cold space: along exterior walls, in crawl spaces, unheated garages, and attics, in sink cabinets on outside walls, and where the water service enters through the foundation.

If one faucet is affected, check the others. When one pipe freezes, others often have too, and it helps you narrow down where the ice is. If no faucet in the house works, the freeze may be near where the main line comes in, or the problem may be the utility's; a neighbor with no water points to the second.

What to Do First

1. Keep the faucet open. Leave the affected faucet open. As the ice melts, water starts moving, and running water helps melt the rest. The open faucet also gives pressure somewhere to go. The Insurance Institute for Business & Home Safety (IBHS) notes that pressure building up between the ice and the faucet is what actually bursts pipes.
2. Know where the main shutoff is before you start. If the pipe has split, water comes out at full pressure the moment the ice lets go. Find the valve, make sure it turns, and keep the path to it clear. Our main shutoff guide shows where it usually is and how to close it.
3. Check for a split before you thaw. Look along every section of the pipe you can see for cracks, bulges, and wet spots, and check the ceiling and walls below. If you find a split or any sign of a leak, shut off the main first and call a plumber. Thawing a split pipe with the water on only starts the leak.

How to Thaw a Frozen Pipe Safely

1. Start at the faucet end. Begin warming the pipe close to the open faucet and work back toward the frozen section. Melting water then has an open path out through the faucet instead of getting trapped behind the ice.
2. Use gentle heat. The Red Cross lists four safe options: an electric heating pad wrapped around the pipe, an electric hair dryer, towels soaked in hot water and wrapped around the pipe, or a portable space heater kept away from anything flammable. The CDC's advice is the same: thaw slowly with warm air from a hair dryer. With a space heater, follow the rules in our winter guide: 3 feet from anything that can burn, plugged straight into a wall outlet, and never left unattended. Plug heating pads, hair dryers, and heaters into a GFCI-protected outlet where you can, keep them and their cords out of the drip path and away from any water, and do not use them while standing in water or on a wet floor.
3. Never use an open flame. No blowtorch, propane or kerosene heater, charcoal stove, or any other open-flame device, per the Red Cross; the CDC says never thaw pipes with a torch. A flame can start a fire inside the wall, rapid, uneven heating can make the pipe burst, and fuel-burning heaters produce carbon monoxide indoors.
4. Keep going until full pressure returns. The Red Cross guidance is to apply heat until full water pressure is restored. A trickle means ice is still in the line.
5. Watch for leaks as it thaws. Keep an eye on the pipe and on the ceiling and walls below it. If water appears anywhere it should not, close the main shutoff.
6. Know when to stop. The Red Cross says to call a licensed plumber if you cannot find the frozen area, cannot reach it, or cannot thaw it. While you wait, turn the heat up and open the cabinet doors on that wall so warm room air can reach the plumbing.

If a Pipe Bursts

1. Shut off the main water valve. This comes first, unless reaching it means stepping into water that could be touching outlets, cords, appliances, or the electrical panel. In that case stay out of the water, call your water utility to close the valve at the curb, and call your electric utility or an electrician to cut the power. Once the main is closed, open a cold faucet on the lowest floor to drain the lines and relieve the pressure behind the break.
2. Deal with the electricity. If water is near outlets, cords, appliances, or the electrical panel, turn off power to that area at the breaker panel, but only if you can reach the panel standing on a dry floor, with dry hands. If you would have to stand in water or on a wet floor to reach the panel, do not touch it: stay out of the water and call an electrician, or your electric utility if you need the power cut at the meter.
3. Call a plumber and your insurer. The plumber repairs the pipe. The insurer can explain what your policy covers and may be able to send a water-removal company, and most policies expect you to take reasonable steps to limit further damage: move belongings out of the water, mop up, and get air moving.
4. Document the damage. Take photos and video of the break, the water, and damaged belongings before you clean up. Keep the damaged section of pipe if you can, and keep receipts for emergency repairs and drying.
5. Dry it out quickly. The EPA's guidance on mold is to clean up and dry water-damaged areas within 24 to 48 hours. Soaked drywall, insulation, and carpet pad usually need a professional water-removal company.

When to Call a Pro

Call a plumber for any burst or leaking pipe, a frozen section you cannot find or reach, a pipe you cannot thaw, or a run that freezes every winter, which usually needs rerouting, insulation, or better air sealing. Call an electrician if water reached the panel, outlets, or wiring; keep the power to that area off until it has been checked. Call your insurer the same day as a burst.

Prevent It

• Insulate pipes in unheated spaces with foam sleeves: crawl spaces, garages, attics, and along exterior walls. The Red Cross, CDC, and IBHS all put this first. Sealing gaps where pipes pass through exterior walls and around the rim joist keeps cold air off them.

• Open sink cabinet doors on exterior walls during cold snaps so warm room air reaches the plumbing, and move cleaners and chemicals out of reach of children and pets first.
• Let faucets drip during hard freezes. When temperatures drop well below freezing, let cold water drip from faucets on exterior walls or served by exposed pipes. This applies to faucets on vulnerable runs, not every tap in the house.
• Keep the heat on. Keep garage doors closed if water lines run through the garage, and hold the thermostat at the same temperature day and night during extreme cold. When you are away, keep the heat no lower than 55°F, the Red Cross minimum. For long trips in cold weather, also shut off the main and drain the lines.
• Winterize the outside. Disconnect and drain garden hoses and close and drain outdoor faucets before the first hard freeze; our outdoor faucet guide walks through it. An in-ground sprinkler system needs its own shutoff and drain or blow-out; see how to winterize a sprinkler system.
• Use heat cable only as its manufacturer specifies. On a pipe that freezes despite insulation, a heat cable listed by a recognized testing lab such as UL or CSA, thermostatically controlled or self-regulating, can help; our heat tape guide compares them. Install it exactly per its instructions, including which pipes it is rated for, whether it may overlap, what insulation may cover it, and what outlet it needs; nVent RAYCHEM, for example, requires ground-fault protection on every circuit feeding its FrostGuard cable. Heat tape is a known fire source when it is old or misinstalled, so replace it once the jacket cracks.
• Add a leak sensor, ideally one with a freeze alert. A sensor under the sink or near the water heater tells you about a leak the moment it starts. Some models also sense temperature and warn you when a space gets cold enough to freeze; the kit below detects water only, so if you want the freeze warning, our leak detector guide covers the models that have it.

Frequently Asked Questions

Should I turn off the water if a pipe is frozen?

If you have found a split or a leak, yes: shut off the main before you thaw. If there is no sign of damage, leave the water on and the faucet open while you thaw, because moving water helps melt the ice. Either way, find the main shutoff first so you can close it in seconds if the pipe starts leaking.

Will frozen pipes thaw on their own?

They can, once the weather warms, but a pipe that split while frozen will then start leaking whenever it thaws, possibly while you are asleep or away. Thawing it deliberately, with the faucet open and you watching, means you are there when the water starts moving.

Can I use a space heater to thaw a frozen pipe?

Yes. The Red Cross lists a portable space heater as a safe option, kept away from anything flammable. Keep it 3 feet from anything that can burn, plug it straight into a wall outlet, and stay with it. Never use a propane or kerosene heater, a charcoal stove, or any open flame.

Does homeowners insurance cover burst pipes?

Many policies cover sudden water damage from a burst pipe, but coverage varies, and insurers can deny a claim when a pipe froze because the heat was left off in an empty house. Read your policy before winter, and call your insurer the day a pipe bursts.

The Bottom Line

Keep the faucet open, find the main shutoff, and check for a split before you apply heat. Thaw gently from the faucet end back, never with a flame. If the pipe has burst, shut off the main, keep clear of wet electrical equipment, call a plumber and your insurer, and document everything. Then insulate the pipe, drip vulnerable faucets in hard freezes, and keep the heat at 55°F or higher when you are away.

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