How to keep pipes from freezing in a cold snap
To keep pipes from freezing when the forecast nears 20°F, keep the heat steady, open cabinet doors on outside walls and let cold water drip from faucets on exposed pipes. Keep the house at 55°F or warmer if you leave. If a tap only trickles, leave it open and thaw the pipe gently from the faucet end.
When to act to keep pipes from freezing
Researchers at the University of Illinois Building Research Council set an alert threshold of 20°F for uninsulated pipes in an uninsulated space, as reported by Armed Forces Insurance. Treat that as a trigger. Pipes in well-insulated walls can do better, and a pipe sitting in a draft can do worse.
| When | What to do |
|---|---|
| Before the first freeze | Disconnect and drain hoses. Close the indoor valve for exposed outdoor lines and drain them. |
| Forecast near 20°F | Drip faucets, open cabinet doors, shut the garage door. |
| Leaving home in cold weather | Set the heat no lower than 55°F. |
| Temperature back above 20°F | Turn the drips off and close the cabinets. |
What you need to prevent frozen pipes
- A flashlight, to see which pipes run through cold spaces
- Pipe insulation for anything exposed
- A hair dryer and old towels for thawing
- A bucket and mop, in case a pipe leaks as it thaws
How to keep pipes from freezing in a cold snap
- Find your weak spots
Trace pipes that run along outside walls and through the garage, crawl space or attic. Those are the ones to protect first.
- Hold the heat steady
Don't turn the thermostat down at night during a cold snap. Armed Forces Insurance suggests 68°F or higher when you're home, and no lower than 55°F while you travel.
- Open up the cabinets
Open sink cabinets on outside walls so room air reaches the pipes. Move cleaners out of reach of children and pets.
- Drip the right faucets
Let a slow, steady drip of cold water run from faucets on exposed lines. If you only drip one, Hunker suggests the faucet farthest from where water enters the house.
- Thaw from the faucet back
Keep the tap open and start nearest the faucet, working toward the frozen part. Use a hair dryer or towels soaked in hot water, so melted water can escape as you go.
- If a pipe bursts, shut the water off first
Close the main valve right away, then call a plumber. Get as much water out as you can to limit mold and damage, and take photos for your insurer.
Signs of frozen pipes
- A trickle from a tap that normally runs well. That suggests a frozen pipe.
- A faucet that was dripping and then stops. Ice may be blocking the line, so keep it open to give pressure somewhere to go.
- Water stains, a bulge in a wall or the sound of running water with every tap closed. Shut off the water at once.
- No water anywhere in the house. The freeze may be at the point where the line enters the house, which is a job for a plumber.
Pipes often burst from the pressure that builds between the ice and a closed faucet, so the split may show up well away from the frozen spot. That's why an open tap helps.
Thaw a frozen pipe yourself or call a plumber?
Prevention and gentle thawing are DIY. Call a licensed plumber if a pipe has burst, if you can't find or reach the frozen section, or if it doesn't thaw.
Stay safe while you work. Never use a torch or any open flame on a pipe. Don't run a hair dryer near standing water, because of the shock risk. Don't heat the house with a gas stove or oven, which raises the risk of fire and burns. Generators and grills stay outdoors, and you should have working carbon monoxide detectors on every level.
How to keep pipes from freezing, according to homeowners
If a garage or workshop has water lines, don't let it drop below freezing to save on heat. One owner turned the garage heat off, then a cold snap cracked a pipe. The water ruined stored photos, and the cold also killed a second fridge kept out there. (Reddit)
Insulate exposed cold-water pipes before fall, not during the first cold snap. (Reddit)
The frozen pipe isn't what wrecks the house. The water pouring out after it thaws is. Before a deep freeze, owners make sure everyone knows how to shut the water at the main or street and where to drain the lines. One Irish owner credits a dripping faucet for keeping their pipes from freezing. (DIY Stack Exchange)
Questions about frozen pipes
At what temperature do pipes freeze in a house?
There's no single number. Research reported by Armed Forces Insurance sets an alert threshold of 20°F for uninsulated pipes in an uninsulated space. Insulation, wind and how long the cold lasts all change the risk.
Should I drip hot or cold water to stop pipes freezing?
Use a slow, steady drip of cold water. Focus on faucets served by pipes along outside walls or in unheated spaces, and keep going until temperatures climb back above 20°F.
How do I thaw a frozen pipe safely?
Leave the faucet open and warm the pipe with a hair dryer or hot wet towels, working from the faucet end. Never use an open flame, and don't use a hair dryer near standing water. Call a plumber if you can't reach the frozen section.
Sources: afi.org, hunker.com, 710keel.com, Ready.gov
General guidance for U.S. homes, not professional advice. For gas, electrical and structural work, call a licensed pro.