How to Thaw a Frozen Pipe Safely (and What Not to Do)

If a faucet only trickles, or nothing comes out on a cold morning, a pipe has probably frozen somewhere along its run. Leave the faucet open, find the cold spot, and warm it gently with a hair dryer, a heating pad or warm towels. Never use an open flame, and know where your main shutoff is before you start, because a frozen pipe may already be cracked.

Why pipes freeze and split

Pipes freeze where they run through cold spaces: outside walls, crawl spaces, attics, garages, and under sinks on exterior walls. Water expands as it freezes, which can split a pipe, but the leak often doesn't show until the ice melts. That's why thawing is also the time to watch closely for water.

Opening the faucet gives melting water somewhere to go and relieves pressure. Warm the pipe starting from the faucet end and work back toward the frozen section, so the water that melts can flow out.

Where pipes freeze

Pipes in outside walls

Especially behind kitchen and bathroom sinks.

Unheated spaces

Crawl spaces, attics, garages and unheated basements.

Outdoor faucets and lines

Hose bibs and irrigation lines left full of water.

Gaps in insulation

Cold air leaking onto a pipe through a small opening.

Frozen, or something else?
What you notice	Likely cause	What to do
One faucet trickles on a cold morning	A frozen pipe to that fixture	Open it and warm the pipe.
Frost or a bulge on a pipe	A frozen section, possibly cracked	Warm it gently; watch for leaks.
No water anywhere in the house	Frozen main line, or a utility problem	Call a plumber or the water utility.
Water spraying or dripping as it thaws	A split pipe	Shut off the main water now.

No open flamesNever use a torch, a propane or kerosene heater, charcoal or any open flame to thaw a pipe. It's a fire and carbon monoxide risk, and it can damage the pipe. Keep hair dryers and space heaters away from water, and plug them into a GFCI-protected outlet where you can. Never leave a space heater running unattended, and don't set it or its cord on wet ground.

Let's fix it

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Open the faucetOpen the faucet the frozen pipe feeds, both hot and cold on a mixing faucet. Melting water needs somewhere to go, and a steady trickle tells you when it's clearing.
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Find the frozen sectionFollow the pipe back from the faucet and look for frost, a bulge, or the coldest spot, often in an outside wall, a crawl space or the cabinet under a sink. Open cabinet doors to let warm room air in. If you can see a split or a bulge, turn off the main water before you warm it; the leak starts as soon as the ice melts.
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Warm it gentlyAim a hair dryer at the pipe, starting nearest the faucet and moving back toward the frozen spot, or wrap it with an electric heating pad or hot, wrung-out towels. Keep the heat gentle and moving.
Done
Watch for leaks as it thawsKeep a flashlight on the pipe and a bucket nearby. If water sprays or drips from the pipe itself, turn off the main water shutoff right away.
Done
Keep it flowingOnce full pressure returns, let the water run for a few minutes, then check every faucet in the house. More than one pipe may have frozen.
Done

If you can't reach the frozen spot

If the frozen section is inside a wall, turn up the heat, open the nearby cabinets, and set a space heater a safe distance from the wall. If that doesn't do it, call a plumber; the wall may need to be opened.

If no faucet in the house has water, the freeze may be where the main line comes in. Call a plumber, or your water utility if you're not sure the problem is on your side of the meter.

Keep it from happening againOn very cold nights, open the cabinet doors under sinks on outside walls and let those faucets drip. Insulating pipes in crawl spaces, garages and attics prevents most freezes.

Keep it from coming backInsulate pipes in crawl spaces and garages, open sink cabinets on outside walls on very cold nights, and disconnect garden hoses before the first freeze.

Renting?If you rent, tell your landlord right away about frozen or burst pipes; repairs and water damage are usually theirs. Shutting off the water to stop a leak is always fine.

Call a plumber ifA pipe has split or is leaking, you can't find or reach the frozen section, the frozen pipe is inside a wall or ceiling, or several pipes are frozen at once.

What a pro typically charges (a rough estimate; prices vary by area): A plumber typically charges $150–$400 to thaw frozen pipes, and more to repair a burst pipe and any water damage.

Something else going on?

Frozen pipe questions

Should I leave the faucet on while thawing a pipe?

Yes. An open faucet lets melting water flow out and shows you when the pipe is clear.

Can I pour boiling water on a frozen pipe?

It's better not to. A sudden temperature change can crack some pipes, and it's hard to control. Warm towels or a hair dryer are safer.

How long does it take to thaw a pipe?

Often 30 minutes to a couple of hours, depending on the cold and how much of the pipe is frozen.

Will a frozen pipe always burst?

No, but the ice can build pressure that splits it. Watch it closely as it thaws, with the main shutoff within reach.

Should I drip faucets on cold nights?

Letting a faucet on an outside wall drip can help prevent a freeze, and opening cabinet doors lets warm air reach the pipes.

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About the authors

GrabTheHammer Team

We're a small team of writers and editors who check every guide against manufacturer instructions and common code requirements. Our goal is to help you understand the problem, tackle what you safely can and know when to call a pro.

Checked against: Manufacturer instructions for the parts and products involved, U.S. Consumer Product Safety Commission.

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A helpful next stepWinterize an outdoor faucetTake the hose off, shut off and drain the line before a hard freeze.

Thaw a frozen pipe safely