How to Thaw Frozen Pipes Safely (Before One Bursts)

To thaw a frozen pipe safely, open the faucet the pipe feeds, then apply gentle heat to the frozen section with a hair dryer, heat lamp, or towels soaked in hot water, working from the faucet end back toward the ice. Never use an open flame or a blowtorch. Keep heating until full water pressure returns, and shut off your main valve at the first sign of a leak. Related: outdoor faucet repair.

How to thaw a frozen pipe, step by step

Work in order. The goal is steady, low heat plus an open faucet so melting ice has somewhere to go. Rushing with high heat cracks pipes, and a torch can both start a fire and burst the line. Most reachable pipes clear in 30 to 60 minutes this way.

1. Find the frozen section. Turn on faucets one at a time. The fixture with no flow or a thin trickle sits downstream of the ice. Follow that supply line to the coldest run: an exterior wall, an unheated basement, a crawl space, or the garage. Feel for a pipe that is icy to the touch or shows frost.
2. Open the affected faucet. Turn both hot and cold handles to a slow open position. Running water, even a trickle, speeds melting and, more important, relieves the pressure that makes a frozen pipe split.
3. Shut off the main if you suspect a break. If you see a bulge, a split, or standing water, close the main shutoff valve before you add any heat. Then read our guide on what to do when a pipe bursts.
4. Apply gentle heat to the frozen spot. Start near the open faucet and move toward the coldest part of the run. This lets melt water drain out instead of pooling behind the ice. Keep the heat moving so no single spot overheats.
5. Keep heating until pressure returns. As the ice melts, the trickle grows into a steady stream. Once full flow is back, run the faucet a few minutes to clear the last of the ice slush.
6. Check every other fixture. One cold snap often freezes more than one pipe. Test hot and cold at each faucet, tub, and toilet supply to be sure nothing else is blocked.
7. Call a plumber if you cannot reach it. If the frozen pipe is inside a finished wall or ceiling, or flow does not return after an hour, stop and find a licensed plumber near you before you open a wall or force it.

Heat methods: what is safe and what is not

Safe thawing means low, controlled heat over the whole frozen length. The methods below cover what actually works and what causes fires or cracked pipes. The single hard rule: no open flame of any kind, ever, including a propane torch, which is the leading cause of pipe-thawing house fires.

How to tell a pipe is frozen

A frozen pipe usually announces itself at the faucet: little or no water on a cold morning. Water freezes at 32 degrees Fahrenheit, but pipes typically need a sustained drop toward 20 degrees, the Red Cross alert threshold, before exposed lines freeze, often after six to eight hours in the cold.

Watch for these tells before you assume the water is just off:

• Only a trickle or nothing from a faucet, while other fixtures run fine.
• Frost, condensation, or a visible bulge on an exposed pipe.
• A pipe that feels ice cold and is located on an exterior wall, in the garage, or in an unheated crawl space or basement.
• Gurgling, banging, or whistling from the pipes when you open the tap.
• Sewer or drain odor, which can signal ice in a vent or drain line.

When a frozen pipe has already burst

The dangerous moment is the thaw, not the freeze. A pipe can split while frozen and stay dry until the ice melts, then release a flood. The Insurance Institute for Business and Home Safety notes a burst supply line can pour hundreds of gallons a day into a home. That is why you keep a hand on the main shutoff valve the whole time you thaw.

Signs the pipe cracked rather than just froze:

• A lengthwise split or bulge in the metal or a cracked plastic fitting.
• Water stains, sagging, or dripping on a ceiling or wall below the pipe run.
• A sudden pressure drop at other faucets once the frozen line starts to thaw.
• The sound of running water when every fixture is off.

If you find a burst, shut the main valve, open faucets to drain the system, and start on our what to do when a pipe bursts checklist. A plumber may charge around $500 on average for the repair itself, but the average home insurance claim for frozen-pipe water damage runs well over $10,000 once floors, drywall, and belongings are counted. Speed on the shutoff is what keeps you on the cheaper side of that gap.

How to prevent frozen pipes

Prevention costs a few dollars and beats every thawing method. The core idea: keep vulnerable pipes above freezing and keep water moving. Most of these steps take minutes and matter most for pipes on exterior walls or in unheated space.

• Hold the heat at 55 degrees Fahrenheit or higher, day and night, and even while you travel. Insurers often require this minimum for frozen-pipe coverage.
• Let the faucet farthest from your water line drip during a hard freeze. Moving water resists freezing and the open tap relieves pressure.
• Open cabinet doors under sinks on exterior walls so warm room air reaches the supply lines.
• Insulate exposed pipes in the basement, garage, crawl space, and attic with foam pipe sleeves or UL-listed heat tape.
• Disconnect garden hoses and shut off and drain outdoor spigots before the first freeze.
• Seal drafts near pipes: fill gaps around rim joists, dryer vents, and where lines pass through exterior walls.
• Keep the garage door closed if water lines run through it.
• Know where your main shutoff valve is and that it turns freely, before you need it in a hurry.

Fold these into your fall routine with our seasonal plumbing maintenance checklist so the vulnerable pipes are wrapped and the outdoor spigots are drained before the first cold snap hits.

Frequently asked questions

How long does it take to thaw a frozen pipe?

Most accessible pipes thaw in 30 to 60 minutes with steady, gentle heat and the faucet left open. A deeply frozen pipe inside a wall or an unheated crawl space can take several hours. If water does not start flowing after an hour of heat, the ice may be in a spot you cannot reach, so call a plumber.

At what temperature do pipes freeze?

Water freezes at 32 degrees Fahrenheit, but pipes usually need sustained cold to freeze. The American Red Cross uses 20 degrees Fahrenheit as its alert threshold for exposed, uninsulated pipes. Pipes in unheated garages, crawl spaces, and exterior walls freeze first, often after six to eight hours below that mark.

Will frozen pipes thaw on their own?

Yes, frozen pipes will eventually thaw on their own once temperatures rise above freezing, but waiting is risky. Ice expands and keeps pressure on the pipe wall the whole time it sits frozen, and pipes often crack during a slow, uncontrolled thaw. Actively thawing with the faucet open relieves that pressure and lowers the burst risk.

How do I know if a frozen pipe has already burst?

A burst frozen pipe often shows no water while frozen, then leaks or floods the moment it thaws. Look for a bulge or split in the pipe, frost or a crack on the metal, water stains on ceilings or walls, or a sudden drop in pressure at other faucets. If you find a burst, shut off the main valve immediately.

Should I leave a faucet dripping to prevent frozen pipes?

Yes, letting a faucet drip during a hard freeze is one of the cheapest ways to prevent frozen pipes. Moving water resists freezing and a slightly open faucet relieves the pressure that actually splits pipes. Drip the faucet farthest from where your water line enters the house, and use warm water lines on exterior walls.

Last reviewed: August 2026.