The answer to this question depends on what you mean by “freeze resistant.” PEX (cross-linked polyethylene) is unique in its ability to expand when water freezes inside it and resilient to shrink back to its original size after the water thaws, avoiding fractures and leakage. It is not totally immune to rupturing from the expansion of water freezing inside it, but very resistant, as proved by testing over multiple freeze/thaw cycles.
Water inside uninsulated PEX pipe, however, freezes when the temperature dips below 20º F for a few hours, just like any other pipe material. The difference is that you can’t electrically thaw it like copper pipe. Also, thawing with any kind of high-heat blower is risky. So while PEX pipe will most likely not be damaged by a hard freeze, you may have to wait for it to thaw out on its own or gently warm it slowly before you can get water flowing again. For this reason, manufacturers recommend that PEX be insulated in any unconditioned spaces of freeze-prone parts of the country, the same as other pipe materials.
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Here’s links to a collection of our other blog posts about PLUMBING PIPES:
• Can PEX pipe be connected to a water heater?
• How can I protect my pipes to keep them from bursting during a hard winter freeze in North Florida?
• Can galvanized steel pipe still be used for new water lines in a house?
• How can I tell if I have cast iron pipes in my house?
• Why can't a sanitary tee be used for a horizontal-to-horizontal drain pipe connection?
• What is the difference between green and white sewer drain pipes?
• Is a washing machine drain hose required to be secured at the standpipe?
• What are the abandoned pipes sticking out of the wall in my house?
• What are the code requirements for plumbing vent terminations?
• What are the code requirements for layout of drain piping under sinks?
• What causes a gurgling sound when a bathtub or sink drains?
• What is a "combination waste and vent" in a plumbing system?
• What is a building trap?
• What is a galvanized nipple?
• What are the pipes sticking out near my water valves?
• How do you accurately find a broken water pipe leak under the floor slab?
• What is the difference between water pipe and sewage (waste) pipe?
• Are plastic pipes (PVC, CPVC, and PEX) safe for drinking water?
• Is a hot water faucet handle required to be on the left?
• What is a dielectric union?
• What's that powdery crust on the pipe connections at the water heater?
• If all the plumbing drains have water in them and you can still smell sewer gas, what's causing the problem?
• How can I tell what type of plumbing pipe I have?
• Why is there a flexible accordion pipe under the sink?
• What is the difference between PVC and ABS plumbing pipe?
• What is the difference between water service pipe and water supply pipe?
• What are the pipes on my roof?
• How can I find out what type of water pipe runs underground from the water meter to the house (service pipe)?
• What is a P-trap?
• Why is old galvanized steel water pipe a problem for homebuyers?
• What does polybutylene pipe look like? Why is it a problem?
• Which water pipes are an insurance problem and possibly uninsurable?
• Can you connect CPVC pipe directly to a gas water heater?
Visit our PLUMBING page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.