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Do Frozen Pipes Always Burst? What Really Happens
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How a pipe bursts
- Not where the ice is. The ICC article, quoting IBHS, says ice blockages usually do not break pipes where they form. Pressure builds between the blockage and a closed faucet, and the pipe often bursts where little or no ice exists.
- Two steps. A 1996 University of Illinois Building Research Council report, as quoted by the Plastics Pipe Institute (PPI), says pipe bursting occurs when freezing temperatures create ice blockages, then further ice growth applies dangerously high pressures to a confined water volume. It says the common view, that ice growth simply pushes against the pipe walls, is not correct.
- Why a single blockage is not enough. A conference paper quoted in the same PPI report says pressure does not build up until two separated ice blockages occur, because until then water is pushed back into the mains or forward into the downstream house piping.
- Expansion. Missouri Extension says water expands as it freezes, and expanding water can cause pipes to break.
What that means for you
- A frozen pipe may be cracked and not look it. Missouri Extension says to be prepared for water leaks from pipes that have been frozen for several hours. Texas A&M says the frozen pipe may already be broken and will leak when it thaws.
- The burst may be somewhere else. Because pressure builds between the blockage and a closed faucet (ICC, quoting IBHS), the damage may not be at the frozen spot.
- Pipe material. The Plastics Pipe Institute, a trade group for plastic pipe makers, says PEX tubing typically expands without cracking and in many instances will not burst when frozen. It also says there are installation situations where PEX can fail, such as freezing inside a concrete slab or highly compacted soil, and that freezing should be prevented in any pipe. We did not find an independent source comparing copper, PVC and PEX, so we can't rank them.
What to do
- Open the faucet on the frozen line. Texas A&M says water will start to flow as you treat the frozen area, which helps melt more ice.
- Find your main water valve. Texas A&M says that if the pipe has already burst, turn off the main valve until the leak is repaired.
- Thaw it safely. Texas A&M lists a heating pad, hair dryer, portable space heater or towels soaked in hot water, with cords kept away from water. Never use a blowtorch, kerosene or propane heater, charcoal stove or other open flame. Our thawing guide has the full steps.
- Check for leaks after it thaws, and look at other faucets. Texas A&M says if one pipe freezes, others may freeze too.
- Call a licensed plumber if you can't find, reach or thaw the pipe, or if it leaks (Texas A&M). If it burst, see burst pipe first steps.
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
Do frozen pipes always burst?
No source we opened says they do. The ICC article, quoting the Institute for Business & Home Safety, says an ice blockage usually does not break the pipe where it forms; pressure builds between the blockage and a closed faucet, and the pipe often bursts where little or no ice exists. Missouri Extension says to be prepared for leaks from pipes that have been frozen for several hours, which means a frozen pipe may be cracked even if it has not visibly failed.
Why do frozen pipes burst?
A 1996 University of Illinois Building Research Council report, quoted in PPI TR-52, says a commonly held view that ice growth simply pushes against the pipe walls is not correct. It says bursting occurs when freezing temperatures create ice blockages, and then further ice growth applies dangerously high pressure to a confined volume of water.
Is a pipe that did not burst safe?
Not necessarily. Texas A&M AgriLife Extension says the frozen pipe may already be broken, and it will leak when the water thaws. It says to know where the main water valve is so you can shut it off until the leak is repaired.
Do plastic pipes burst less than copper?
An industry group, the Plastics Pipe Institute, says the elasticity of PEX typically allows it to expand without cracking or splitting, and that in many instances PEX will not burst when the fluid inside freezes. It also says there are installation situations where PEX can fail, for example when pipe freezes inside a concrete slab or compacted soil, and that freezing in any pipe should be prevented. That is a trade group describing its own product.
What should I do with a frozen pipe?
Texas A&M says to keep the faucet open, shut off the main valve if the pipe has burst, and apply heat to the frozen section with a heating pad, hair dryer, space heater or towels soaked in hot water. No open flame. See our thawing guide.
Related guides
- International Code Council eNews: Build It to Code to Minimize Damage from Frozen Water Pipes (early 2014; quotes IBHS guidance)
- Plastics Pipe Institute (a plastic pipe industry trade group): PPI TR-52, Resistance of PEX Pipe and Tubing to Breakage When Frozen, 2026 edition (its section 3.2 quotes the 1996 University of Illinois Building Research Council Research Report 96-1; treat the PEX claims as industry claims)
- University of Missouri Extension: Frozen pipes create big problems during cold weather
- Texas A&M AgriLife Extension: Winter Storms: Preventing and Thawing Frozen Pipes
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.