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How Long Does It Take for Pipes to Freeze? What the Sources Say
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What the sources say
- The temperature. Texas A&M AgriLife Extension says water pipes have the potential to freeze and burst when the outside temperature reaches 20 °F or below. The IBHS, quoted by the International Code Council (ICC), says freezing of unprotected pipes begins to occur when outdoor temperatures drop to 20 °F.
- The place. Texas A&M lists the most vulnerable pipes: outdoor hose bibs, pool supply lines, sprinkler lines, and pipes in basements, crawl spaces, attics, garages and against exterior walls with little or no insulation. Illinois Extension and Missouri Extension both name outer walls, crawl spaces and attics.
- Air leaks. The ICC article, quoting IBHS, says the risk is higher where cracks or openings let cold outside air reach the pipes.
- Heat, not just insulation. The ICC article, quoting IBHS, says insulation by itself (without a heat source) cannot protect a pipe from freezing.
- How long. The ICC article does not say how long temperatures must stay low before pipes fail. Missouri Extension says to be prepared for leaks from pipes that have been frozen for several hours. None of the pages we opened turn that into a rule such as "X hours at Y degrees," and we won't invent one.
Our free checker uses the forecast low, where your pipes run, insulation and heat. It is a rough guide, not a prediction. See the freeze risk checker.
What to do tonight if a hard freeze is coming
- Keep the heat on and steady. Texas A&M says to keep the thermostat at a consistent temperature day and night. Illinois Extension says to set it no lower than 55 °F.
- Open the cabinet doors in the kitchen and bathroom so warm air reaches the plumbing (Texas A&M, Illinois Extension).
- Let a faucet trickle. Illinois Extension says to let hot and cold water trickle from a faucet on an outside wall at night.
- Close the garage door if supply lines are in the garage (Texas A&M).
- Protect exposed pipes. Texas A&M suggests pipe sleeves or UL-listed heat tape or heat cable on exposed pipes, and says newspaper gives only some protection when cold is not frequent or prolonged. Read our heat tape and pipe insulation guide.
- Know your main water shut-off in case a pipe bursts (Texas A&M, Illinois Extension).
If a pipe is already frozen, see how to thaw frozen pipes. Never use an open flame.
Will your pipes freeze tonight?
Answer four quick questions about tonight's low, where your pipes run, insulation and heat setting. Get a risk level and a short to-do list.
Open the freeze risk checkerProtect the pipes before the next cold snap
Pipe sleeves and UL-listed heat cable are the products Red Cross and extension services point to for exposed pipes. Read the label and follow the maker's instructions.
How to choose and use themSee pipe insulation and faucet coversSee UL-listed heat cableCommon questions
How long does it take for pipes to freeze?
None of the sources we opened give a number of hours. They give a temperature instead. Texas A&M AgriLife Extension says water pipes have the potential to freeze and burst when the outside temperature reaches 20 °F or below. The Institute for Business & Home Safety (IBHS), quoted by the International Code Council, says freezing of unprotected pipes begins to occur when outdoor temperatures drop to 20 °F.
Do pipes freeze at 32 degrees?
The pages we opened do not say that 32 °F freezes pipes. Texas A&M and IBHS point to 20 °F as the outdoor temperature where unprotected pipes can begin to freeze. Missouri Extension notes that pipes in unheated spaces and along exterior walls are exposed to severe cold.
Which pipes freeze first?
Texas A&M lists outdoor hose bibs, pool and sprinkler supply lines, and water pipes in basements, crawl spaces, attics, garages and against exterior walls with little or no insulation. Missouri Extension says pipes along exterior walls are especially subject to freezing.
Will pipes freeze if the heat is on?
They can, in cold spots. Illinois Extension says the pipes most susceptible are typically those near outer walls, in crawl spaces or in the attic, and it says to keep the heat on at 55 °F or higher. ICC, quoting IBHS, says insulation without a heat source cannot protect a pipe from freezing.
How can I slow freezing tonight?
Texas A&M says to open kitchen and bathroom cabinet doors so warm air reaches the plumbing, keep the thermostat steady day and night, and keep the garage door closed if supply lines are inside. Illinois Extension says to let hot and cold water trickle from a faucet on an outside wall at night.
Related guides
- Texas A&M AgriLife Extension: Winter Storms: Preventing and Thawing Frozen Pipes
- International Code Council eNews: Build It to Code to Minimize Damage from Frozen Water Pipes (early 2014; quotes IBHS guidance)
- University of Illinois Extension: Water Pipes
- University of Missouri Extension: Frozen pipes create big problems during cold weather
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.