Home Improvement Skills & Specialties Plumbing Plumbing Problems & Repairs

How to Thaw and Prevent Frozen Water Pipes

By

Bob Formisano

Updated on 11/18/24

Reviewed by

Richard Epstein

Fact checked by

Emily Estep

How to prevent and thaw frozen water pipes — The Spruce / Tessa Cooper

In This Article

Why Pipes Freeze
Locate Frozen Pipes
Thaw Pipes in Walls
Thaw Exposed Pipes
Prevent Frozen Pipes
FAQ

Working Time: 1 - 2 hrs
Total Time: 1 - 2 hrs
Skill Level: Beginner
Estimated Cost: $5 to $10

Frozen water pipes are a serious risk during very cold winter weather. When water freezes in a pipe, it expands and can exert pressure at over 2,000 pounds per square inch. That's enough to rupture almost any pipe, since there's nowhere for the ice to expand.

A frozen pipe can be a time bomb, because there may be no leaking—that is, until the frozen water blocking the pipe begins to thaw. If left alone, thawing water from frozen pipes can cause tens of thousands of dollars in major flooding, water damage, destroyed walls, ceilings, and floors.

Why Pipes Freeze

Pipes are most likely to freeze when temperatures drop to 20°F or less, and when temperatures stay below freezing for more than a few days. They're also susceptible to freezing when they are located:

In an outside wall that is subject to freezing outdoor temperatures
In a cabinet under a sink (especially near an outside wall)
In an unheated crawl space or basement
Near outdoor faucets (hose bibs) used to connect garden hoses

If your pipe is frozen but not yet ruptured, you must thaw it right away. There are a few thawing techniques to try, depending on where the frozen pipe is located.

Locating the Frozen Water Pipe

A frozen pipe that hasn't burst yet often reveals itself at a faucet. If you turn on the faucet in very cold weather and no water comes out—or it's slowed to a trickle—there's a good chance the pipe is blocked with ice somewhere. Take immediate action with the steps below:

Shut off the water: Look for the shut-off valve to the faucet or the home's main water shutoff valve.
Open the faucet: Relieve pressure by opening the faucet supplied by the frozen pipe.
Identify the frozen pipe: Locate the blockage by following the pipe from the faucet to where it runs through cold areas, such as exterior walls or unheated crawl spaces.
Locate a frozen blockage: Search for areas of the pipe that have frost or ice; they may also be slightly bulged or fissured.

How you thaw a pipe will depend on where it is located.

What You'll Need

Equipment / Tools

Blow-dryer
Portable heater
Heating pad

Materials

Electric heat tape
Towels
Cookie sheet (optional)

Instructions

Materials needed to prevent and thaw out frozen pipes — The Spruce / Tessa Cooper

How to Thaw a Frozen Pipe Inside a Wall

When you find that a frozen pipe located behind the surface of a wall or ceiling that has not yet burst, it's important to take steps to thaw it immediately in order to prevent structural damage to your home.

Turn Up the Heat

Turn up the heat in the house and wait. If you expect cold weather for a few days, keep the heat up before and during the cold wave. Being a little warm (and having a higher heating bill) is better than having frozen pipes behind walls and costly repairs.
Open Cabinet Doors

If you suspect the pipe is inside the wall within a bathroom, kitchen sink base cabinet, or vanity, make sure to open the door of the cabinet to help heat reach the wall.
Open Up the Wall

If you believe a burst pipe could be imminent, cut out a section of the wall or ceiling to access the frozen section of pipe, then thaw the pipe as if it were an exposed pipe.

How to Thaw a Frozen Exposed Pipe

If the frozen pipe is exposed, like in an unfinished basement or garage, you have several options for thawing it. No matter what technique you use, always heat the pipe from the faucet side first, moving toward the frozen area. This allows water to flow out as the ice melts.

Warning

Never use a blow torch or other open flame to thaw a pipe. This presents a serious fire hazard and can damage the pipe.

Try a Blow-Dryer

A blow-dryer is usually the easiest and safest way to thaw a pipe. If the pipe is close to the wall, you can also place a cookie sheet behind the pipe to help radiate heat from the wall onto the backside of the pipe.

The Spruce / Tessa Cooper
Set Up a Portable Heater

A small, powerful heater works great for warming pipes under a kitchen sink or in a vanity cabinet. Direct the heater onto the frozen section of the pipe, making sure to keep an eye on the heater as you use it on the pipe.

The Spruce / Tessa Cooper
Use Electric Heat Tape

Heat tape is a ribbon-like wrap that contains electrical heating elements, and is controlled with a thermostat. Wrap it around the pipe you want to heat, and plug it into the wall.

Tip

Heat tape can also be left on pipes year-round and plugged in when needed to help prevent freezing in critical areas.

The Spruce / Tessa Cooper
Use a Heating Pad

An electrical heating pad can also be used to thaw pipes. Plug the pad in and wrap it around the pipe, slowly moving it from the faucet to the blockage as the water starts to thaw. You can also soak towels in hot water and wrap them the same way if needed—just make sure to keep swapping them out as they cool.

How to Prevent Frozen Pipes

There are a few things you can do to prevent the problem of freezing pipes from occurring again:

Leave the faucet dripping: Steadily moving water will keep the pipes slightly above the freezing point, and prevent them from freezing.
Leave the heat on: If temperatures are expected to drop below freezing, run your heater at a consistent 55°F minimum, both day and night.
Keep cabinet doors open: Open cabinet doors will allow the heated air from the room to reach pipes inside the cabinet. This is often enough to prevent kitchen pipes from freezing on the coldest nights.
Keep heat tape on: Leave the problem pipe wrapped in electrical heat tape, and plug it in when the weather is especially cold.
Insulate pipes: Use foam insulation wrap to provide a layer of protection for pipes that run through unheated spaces. This will help slows the transfer of heat, but cannot prevent a pipe from freezing if the surrounding air is cold enough.
Install a heater: It's worth investing in a permanent heater (such as a baseboard heater) to keep areas with pipes above the freezing point. Do not use portable heaters for this purpose; they should never be left unattended.

Protect outdoor faucets: Remove garden hoses attached to outdoor faucets. If the faucet is not frost-proof, winterize the pipes by turning off water to the faucet inside the house, draining the exterior section of the pipe and faucet, and placing outdoor faucet covers over exposed faucets.
Check for leaks: Make sure there are no leaks in or around your pipes. Check the pipes themselves for cracks or joints that need replacing, and ensure there are no air leaks in the areas around them.
Seal cracks: If you do find any air leaks, seal them with caulk to prevent cold air from entering.
Call a plumber: Having a plumber regularly check your pipes for leaks can help prevent water from freezing inside. A plumber can also help you identify and seal air leaks, place insulation around your existing pipes, or replace them with a more resilient, frost-resistant material.

FAQ

Do frozen pipes thaw on their own?

Yes, frozen pipes will eventually thaw on their own—but allowing them to do so can cause them to burst, so it's important to thaw a frozen pipe yourself.
How long does it take for frozen pipes to unfreeze?

Gradually unfreezing a frozen pipe with a blow-dryer, portable heater, heat tape, hot towels, or a heating pad will typically take 30 minutes to an hour.
How do plumbers unfreeze pipes?

When you call a plumber, they will use a heat gun to unfreeze the pipes in your home safely and efficiently.