At What Temperature Pipes Freeze, and Why There Is No Single Number
Fresh water freezes at 32°F, according to NOAA. But there is no single outdoor temperature at which every pipe freezes. Whether a pipe freezes depends on where it runs, how well it is insulated and protected from drafts, and how long the cold lasts, according to the American Red Cross and the National Weather Service (NWS).
The Insurance Institute for Business and Home Safety (IBHS) says exposed pipes, crawl spaces and outdoor hose spigots are vulnerable once temperatures drop below freezing. So the frozen pipes temperature to watch is not one number on a thermometer. It is a mix of how cold it gets, how long it stays that way, and how protected your pipes are.
You may see websites that give a specific outdoor temperature or a number of hours before pipes freeze. We do not repeat those figures here, because we could not tie them to a public agency source.
What the Forecast Words Mean
Two forecast terms are worth knowing. They come from the NWS glossary:
- Freeze: the surface air temperature is expected to be 32°F or below over a wide area for a significant period.
- Hard freeze: the air temperature reaches 28°F or lower for an extended period.
Treat either forecast as your signal to take the steps in our checklist on how to prevent frozen pipes. A hard freeze forecast is not the point at which pipes freeze. It is a reminder to get ready.
What Makes One Pipe Freeze Before Another
Two pipes in the same house can behave very differently in the same cold snap. These are the factors the sources point to:
- Where the pipe runs. The American Red Cross says the pipes that freeze most often are those exposed to severe cold (outdoor hose bibs, pool and sprinkler lines), those in unheated areas (basements, crawl spaces, attics, garages and kitchen cabinets), and those along exterior walls with little or no insulation.
- Insulation. The American Red Cross says insulation keeps attics, basements and crawl spaces warmer. IBHS says to insulate pipes in hard-to-reach places and along walls facing outside.
- Wind and drafts. The NWS says wind does not cool a pipe below the actual air temperature, but it shortens the time the pipe takes to cool. IBHS says to seal cracks and gaps and to cover ventilated crawl spaces in winter.
- How long the cold lasts. The NWS defines a hard freeze by temperature over an extended period. The longer exposed pipes sit in below-freezing air, the more time they have to cool.
- Heat inside the house. IBHS says plumbing may freeze in extreme cold, particularly during power outages, and that a broken heating system can make a home dangerously cold and cause pipes to freeze. Our guide on how to keep pipes from freezing without heat or power covers what to do when the heat is out.
The Indoor Temperature That Helps Protect Pipes
The thermostat is one thing you control. The American Red Cross says to keep the thermostat at the same temperature day and night, and that if you go away in cold weather you should leave the heat set no lower than 55°F. IBHS says to set the thermostat to at least 55°F to keep pipes from freezing, even when no one is home. The EPA says not to set the indoor temperature too low.
Heat inside is not the whole answer. Pipes in unheated spaces are the ones the American Red Cross says freeze most often, so they need insulation even when the thermostat is set correctly.
Is There a Temperature at Which Pipes Burst?
No. Pipes break because water expands as it freezes. The American Red Cross says this puts tremendous pressure on metal or plastic pipes and that, no matter the strength of a container, expanding water can cause pipes to break. The NWS says water expands as it freezes, causing pipes to burst.
Because a frozen pipe can break, watch it and the area around it for leaks as it thaws and water flows again, and know where your main shutoff is so you can close it at once if a leak appears (EPA, IBHS). Our guide on how to unfreeze pipes safely and check for a burst explains what to watch for as a pipe thaws.
What to Do When a Freeze Is Forecast
When a freeze is in the forecast, here are the quick steps. The full list is in our pre-freeze checklist for your pipes.
- Let cold water drip from faucets served by exposed pipes, and open cabinet doors (American Red Cross). No agency gives a temperature at which to start dripping faucets.
- Keep the thermostat steady and at least 55°F (American Red Cross, IBHS).
- Disconnect and drain outdoor hoses and shut off outdoor spigots (American Red Cross, EPA).
- Know where your main water shutoff is (IBHS).
When a Frozen Pipe Turns Into Water Damage
If a pipe froze and burst or leaked into walls, ceilings or floors, the plumber repairs the pipe and a water damage professional removes the water and dries the structure. The EPA says that if pipes burst and walls and flooring are wet, you should fix the leak promptly and dry everything completely. It says to dry water-damaged areas within 24 to 48 hours to prevent mold growth.
We handle the water and drying side. Read more about our frozen pipe water damage service, or see our full water damage restoration work. We offer 24/7 emergency restoration service, so if a frozen pipe has already leaked, call Romexterra Restoration at (312) 549-9620.
