Frozen pipes: prevention and what to do if it happens
Which pipes freeze first, the steps that prevent it, what to do the moment a faucet runs dry, and the point where this becomes a job for a plumber.
By Elijah Canfield, Founder, Hire Best Pros · Updated September 10, 2026
Elijah Canfield is the founder of Hire Best Pros. He writes and edits the site's consumer guides, with a focus on how home service and moving projects are priced, scoped and compared.
Pipes freeze where water sits still in an unheated space, so prevention is mostly about heat, insulation and airflow. If a faucet suddenly runs dry in freezing weather, shut off the main water valve first, then warm the line gently while the tap stays open. Never use an open flame, and call a plumber if you cannot reach the frozen section or you suspect the pipe has already split.
Key points
- Exterior walls, crawl spaces, attics, garages and unheated basements are where freezes usually start.
- Know where your main shutoff valve is before winter, not during an emergency.
- Thaw gently with warm air or towels. An open flame is a fire risk and can damage the pipe.
- A split pipe often does not show itself until the ice thaws, so watch the line as it comes back.
Why pipes burst
Water expands as it freezes. The damage usually is not caused at the ice itself, but by the pressure that builds between the ice plug and a closed faucet downstream. That trapped pressure is what splits copper or cracks a fitting.
This is why letting a faucet drip during a hard freeze helps. It relieves pressure and keeps water moving in the line most at risk.
Where freezes start
Look for plumbing that runs through space you do not heat, or against surfaces that get cold from the outside.
- Pipes in exterior walls, especially under kitchen and bathroom sinks
- Crawl spaces, unheated basements and attic runs
- Garage plumbing and utility sinks
- Outdoor hose bibs left connected to a hose
- Lines in vacant or seasonal properties with the heat turned down
Prevention before the cold arrives
Most of this is a weekend of small work that pays for itself the first time a cold snap lands.
- Disconnect and drain garden hoses, then shut off and drain exterior spigots
- Insulate pipes in unheated spaces with foam sleeves rated for the job
- Seal drafts where lines pass through rim joists, foundation walls or crawl space vents
- Open cabinet doors under sinks on exterior walls so household heat reaches the pipes
- Keep the thermostat steady day and night, and no lower than the mid fifties if you travel
- Have heat tape or heat cable installed by a professional where a run keeps freezing
Want the rest of the seasonal list?
See the year round home maintenance checklistWhat to do the moment a faucet runs dry
A tap that sputters and stops in freezing weather is the signal. Move quickly but calmly, because your goal is to reduce pressure and add gentle heat.
- Locate your main shutoff valve and be ready to close it
- Leave the affected faucet open so melting water has somewhere to go
- Warm the pipe with a hair dryer, a space heater at a safe distance or warm towels, working from the faucet back toward the frozen section
- Open cabinet doors and add heat to the room around the pipe
- Check other fixtures, because if one line froze others are probably close
What not to do
Never use a propane torch, kerosene heater or any open flame on a pipe. It is a serious fire risk in a wall cavity and can damage the pipe or the solder joints even when it appears to work.
Do not leave a space heater unattended near cabinets or towels, and do not keep running water at a fixture you cannot see if you suspect the line has already split.
When to call a plumber
Call if you cannot locate the frozen section, if it runs inside a wall or under a slab, if the pipe does not thaw with gentle heat, or if water appears anywhere once flow returns. A hidden split can soak framing and insulation long before it shows on a ceiling.
If water is already escaping, shut off the main valve first and then call. Stopping the flow matters more than diagnosing the cause.
Need help with a frozen or burst line?
Find a plumbing professionalAfter the thaw
Watch the pipe and the area around it for a full day. Look for damp drywall, stained ceilings, warm spots on floors and any drop in pressure at the fixture.
If a freeze happened once, treat the cause rather than the event. Insulation, air sealing or rerouting a vulnerable run is the fix that stops next winter from repeating this one.
Common questions
- At what temperature do pipes freeze?
- There is no single number, because it depends on how long the cold lasts, how exposed the pipe is and how much heat reaches it. Uninsulated pipes in unheated spaces are at risk once outdoor temperatures sit below freezing for several hours, and wind makes that happen faster.
- Should I leave faucets dripping in a freeze?
- A slow drip on fixtures served by vulnerable pipes is a reasonable precaution during a hard freeze. Moving water is slower to freeze and the open faucet relieves the pressure that actually bursts pipes. Choose the taps on exterior walls or at the far end of the run.
- How long does it take to thaw a frozen pipe?
- Gentle heat on an accessible pipe often restores flow within an hour, though a long or deeply chilled run can take longer. If nothing changes after a sustained effort, or the pipe is inside a wall, stop and call a plumber rather than adding more heat.
- Does home insurance cover a burst pipe?
- Many policies cover sudden water damage from a burst pipe while excluding damage tied to neglect, such as an unheated home. Terms differ by policy and state, so read your own coverage and ask your insurer what they expect from you during freezing weather.