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Hot Water Pipe Frozen but Cold Water Works? What to Check
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Why a hot line can freeze
- It is still a water pipe. Texas A&M says a hot water supply line can freeze if water is not running through the pipe and the water temperature in the pipe is cold. It tells you to check unheated spots: the basement, crawl space, attic, garage and under kitchen and bathroom cabinets.
- It can happen next to a cold pipe that is fine. A 1980 University of Alaska Fairbanks Geophysical Institute column says hot water pipes exposed to freezing temperatures can freeze and burst while identical cold pipes beside them stay intact. Its explanation is a leading idea, not settled science, and the same column says cold water pipes really do freeze before hot ones.
What to do
- Open the faucet on the affected line. Texas A&M says water will begin to flow as you treat the frozen area, which helps melt more ice.
- Know where the main valve is. Texas A&M says the frozen pipe may already be broken and will leak when it thaws. If so, turn off the main water valve until the leak is repaired.
- Apply heat to the frozen section. Texas A&M lists a heating pad, an electric hair dryer, a portable space heater, or towels soaked in hot water. Keep electrical cords away from water. Apply heat until full water pressure is restored.
- No open flame. Texas A&M says not to use a blowtorch, kerosene or propane heater, charcoal stove or other open flame. They are a fire hazard and release lethal carbon monoxide.
- Check other faucets. Texas A&M says that if one pipe freezes, others may freeze too.
- Call a licensed plumber if you can't locate the frozen area, can't reach it or can't thaw it.
See also our full guide on how to thaw frozen pipes and what to do when pipes freeze.
Can't find it, can't reach it or can't thaw it?
The Red Cross says to call a licensed plumber if you can't locate the frozen area, can't reach it, or can't thaw the pipe. Burst pipes also need a plumber.
When to call a plumberFind a licensed plumber near youCommon questions
Can a hot water pipe freeze?
Yes. Texas A&M AgriLife Extension says a hot water supply line can freeze just as a cold one can if water is not running through the pipe and the water in it is cold.
Why would the hot pipe freeze but not the cold one next to it?
A 1980 column from the University of Alaska Fairbanks Geophysical Institute says hot water pipes exposed to freezing temperatures can freeze and burst while identical cold water pipes beside them stay intact. It explains this with a leading idea, not a proven fact: heated water behaves differently as it freezes, so the ice forms later but faster and may burst the pipe. It also says cold water pipes really do freeze first. This is an old science column and an explanation under discussion, so treat it as background.
Should I keep the faucet open?
Texas A&M says that if you suspect a pipe is frozen, keep the faucet open. Water will begin to flow as you treat the frozen area, which helps melt more ice.
Can I use a torch or open flame to thaw it?
No. Texas A&M says not to use a blowtorch, kerosene or propane heater, charcoal stove or other open flame devices. They are a serious fire hazard and release lethal carbon monoxide fumes.
When should I call a plumber?
Texas A&M says to call a licensed plumber if you are unable to locate the frozen area, if the frozen area is not within reach, or if you can't get the pipe to thaw.
Related guides
Free printable: Frozen Pipe Night-Before Checklist
What to do before a cold night so your pipes survive it. Download the one-page PDF now, or get it by email along with a short series of five helpful emails.