How to thaw frozen pipes safely

Key takeaways

• Open the faucet the frozen pipe feeds before you apply any heat. Melting ice needs somewhere to go, and an open tap relieves pressure.
• Warm the pipe slowly, starting at the faucet end and working back toward the freeze. A hair dryer, warm towels or a space heater kept at a safe distance all work.
• Never use an open flame, a torch, or a charcoal or propane heater indoors.
• Check for leaks as the pipe thaws. A crack you can't see starts leaking the moment the ice melts.
• If water is spraying or pooling, shut off the main valve and call a plumber.

Is the pipe frozen?

Signs you are dealing with a frozen pipe and not something else:

• One faucet gives a trickle or nothing, while others work.
• No water anywhere in the house, on a morning when it is below freezing.
• Frost or a bulge on a pipe you can see.
• A toilet that won't refill.

If the whole house has no water, the problem may be a frozen supply line or something outside your control, such as a utility outage. Work through no water in the house first to sort out which it is.

Step by step: thaw a frozen pipe

1. Open the faucet. Open the tap the frozen line feeds. Open both hot and cold if you aren't sure. As the ice melts, water has to flow out, and an open tap relieves the pressure.
2. Find the frozen section. Follow the pipe from the faucet. A frozen section often feels colder than the rest. It is usually where the pipe passes through an exterior wall, a crawlspace, a garage or a cold corner. Frost on the outside is a giveaway.
3. Shut off the main water valve if you suspect a split. If you can see a crack, a bulge or wet spots, turn the main off now, before the ice melts.
4. Apply gentle heat to the pipe. Start near the faucet and work back toward the frozen section. This lets melted water drain out as you go.
5. Keep the heat on until water flows normally. Then leave the faucet open a little, with a slow trickle, while the pipe warms up.
6. Check every pipe you can reach for leaks. Look under sinks, in the crawlspace and along walls. Watch for drips, wet insulation and damp drywall for the next hour or two, as the pressure comes back.
7. Find out why it froze. Fix the cause, or it will freeze again tomorrow. The prevention guide lists the usual causes and fixes.

Safe ways to add heat

These are the ways most homeowners can warm a pipe with low risk:

• A hair dryer. Move it back and forth along the pipe. Don't stand in water while you use it.
• Warm towels. Soak towels in hot (not boiling) water, wring them out and wrap them around the pipe. Swap them as they cool.
• A space heater, kept back. Keep it at least 3 feet from anything that can burn, plug it directly into a wall outlet and never leave it running unattended. This is NFPA and U.S. Fire Administration guidance. Don't point it at a wooden joist or insulation.
• Raising the room temperature. Open cabinet doors under the sink so warm air reaches the pipe. Turn the thermostat up.
• An electric heating pad wrapped around the pipe, if it is made for that use.

Keep applying heat until full water pressure returns, then check the other faucets in the house. If one pipe has frozen, others may have too.

What never to use

• A blowtorch or any open flame. The Red Cross advises against both. Fire can damage the pipe and its joints, and it can ignite framing, insulation and anything stored nearby.
• A kerosene or propane heater, or a charcoal stove. The Red Cross lists these too. Fuel-burning heaters indoors also produce carbon monoxide, which is odorless and can kill.

If you smell gas, leave the house and call your gas utility from outside.

Signs the pipe has already burst

Water that was frozen in a split pipe can hold the leak closed until it thaws. Watch for:

• Water spraying or running from a pipe, ceiling or wall as the ice melts.
• A wet spot or stain on drywall or the ceiling that wasn't there yesterday.
• Your water meter moving when every fixture is off.
• The sound of running water you can't trace.
• A pipe that bulges, or has a visible crack or split seam.

If you see any of these, shut off the main valve first, then call. The burst pipe repair page explains what to do in the next few minutes. If you can't find the main valve, or can't turn it, use the curb stop at the meter by the street, if you have the key, and call a plumber. Use the emergency plumber page if it is after hours.

After the pipe thaws

1. Run the water. Let the faucet run for a minute to flush air and any debris.
2. Check for leaks again after an hour, then again after a day. Some cracks open slowly under pressure.
3. Look at the pipe itself. Pinhole leaks, bulges and cracks mean the pipe needs repair. A pipe that froze once is more likely to freeze again.
4. Dry any wet areas fast. The EPA says mold can grow on wood, drywall, carpet and furniture that stay wet for more than 24 hours, so use fans and open windows if the weather allows, and move wet items out of the room. Don't wait for it to dry on its own. If a lot of water got out, see water damage restoration.
5. Take photos of any damage before you clean up. They help if you decide to file an insurance claim.
6. Protect the pipe. Add foam insulation or ask a plumber about heat tape or rerouting.

East Tennessee conditions

The typical last spring freeze at the Tri-Cities Airport is around April 16 (1991 to 2020 data from NOAA and the National Weather Service), so a freeze can come well after the worst of winter feels over. The pipes that freeze are usually those in a vented crawlspace, in an exterior wall, or in an unheated garage. The frozen pipes page covers the common trouble spots in local homes.

When to stop and call a plumber

Stop and call a licensed plumber if:

• You can't find the frozen section, or can't get to it, such as inside a wall or under a slab.
• Water is leaking from a pipe, wall or ceiling.
• The pipe is cracked, bulging or split.
• You've been trying for an hour and nothing is moving.
• The frozen line is a main supply line, a well line, a gas line, or part of a heating system.
• You aren't comfortable working near electricity or wet floors.

Make the call early. A pipe that has burst gets worse every minute the water runs. Tell the plumber which fixture lost water, where you think the pipe is frozen, and whether you can see any damage.

How long to keep trying

Give a gentle thaw about an hour. If water has not started to flow by then, stop. The freeze may be somewhere you can't reach, such as inside a wall, under a slab or in a buried line, and more heat in the wrong place only adds risk. Leave the faucet open, keep the room warm, shut off the main if anything is leaking, and call a plumber with the details you gathered.

Keep it from happening again

A pipe that froze once will freeze again in the same conditions. Before the next cold night, add foam insulation, close crawlspace vents, open cabinet doors under the sink and leave a cold trickle running. The prevention guide has a full checklist. Also make sure everyone in the house knows where the main shutoff is, so the water can be stopped in seconds if a pipe splits.

Safety

• Water and electricity don't mix. Keep hair dryers and heaters away from standing water, and don't touch outlets or cords with wet hands. If water is near an outlet or the panel, stay away and turn off power at the breaker only if you can reach it dry.
• Fire. Never use an open flame. Keep anything hot at least 3 feet from combustible material.
• Slips. Thawing makes wet floors. Wipe up water as you go.
• Carbon monoxide. Never use a fuel-burning heater indoors. Make sure you have a working carbon monoxide alarm.