The short, crucial answer is yes, PEX pipe absolutely can freeze. While PEX
(cross-linked polyethylene) boasts significant advantages over traditional metal
pipes like copper, it is not magically freeze-proof. Water expanding as it turns
to ice exerts tremendous pressure, and no common plumbing material is entirely
immune to the laws of physics.
However, understanding how PEX behaves when frozen and why it's often
considered more resilient is key for homeowners in cold climates.
The Freezing Reality: Water Expands
The core problem isn't the pipe material itself initially; it's the water
inside it. When water freezes, it expands by approximately 9%. This expansion
creates immense pressure within the confined space of the pipe. If this pressure
exceeds the pipe's strength, a rupture occurs – a burst pipe.
PEX vs. Copper/Iron: Why the Resilience Hype?
PEX earns its reputation for better freeze tolerance due to two key
properties:
Flexibility and Elasticity: PEX is inherently flexible. When water inside
freezes and expands, the PEX tube can stretch to a certain degree, absorbing
some of the pressure. Think of it like a balloon expanding slightly.
Lack of Splitting Seams: Unlike rigid copper pipes which are soldered
together at joints, or iron pipes with threaded connections, PEX systems
typically use fewer rigid fittings within long runs. Continuous loops or long
stretches of PEX have no weak solder joints or seams that are prone to splitting
under pressure. The pipe itself stretches before a fitting might fail (though
fittings can still be points of failure).
Important Caveats: PEX Can Still Burst
Don't mistake tolerance for immunity. The freeze resilience of PEX has
limits:
Extreme Pressure: If the ice blockage is significant and the pressure
buildup is too high, even flexible PEX will eventually rupture.
Fitting Failures: While the pipe might stretch, the brass or plastic
fittings (elbows, tees, couplings) connecting PEX sections are rigid. These
fittings are often the weakest link and can crack or break under the stress of
ice expansion.
Repeated Freezing: Even if PEX survives one freeze/thaw cycle without
bursting, repeated freezing and expansion can fatigue the material, making it
more brittle and susceptible to failure in the future.
Existing Weak Points: Kinks, damage from UV exposure (before installation),
improper installation, or manufacturing defects create vulnerable spots more
likely to fail.
Protecting Your PEX Pipes: Prevention is Paramount
Relying on PEX's slight resilience is a dangerous gamble. Preventing
freezing is always the best and only reliable strategy:
Insulation is Non-Negotiable: Pipe insulation is the first line of defense.
Use foam sleeves specifically designed for pipes, ensuring a snug fit,
especially in vulnerable areas like attics, crawl spaces, basements, garages,
and exterior walls. Insulation slows down heat loss; it doesn't prevent freezing
indefinitely in severe cold without a heat source.
Seal Air Leaks: Cold air entering through cracks, holes, or gaps around
pipes in exterior walls or foundations dramatically increases freezing risk.
Seal these openings with caulk or spray foam.
Maintain Heat: Ensure areas where pipes run stay above freezing. Keep
garage doors closed, open cabinet doors under sinks on exterior walls during
deep freezes to allow warm air to circulate, and never set your thermostat too
low when away in winter.
Consider Heat Tape (Cable): For pipes in extremely vulnerable, unheated
locations (like crawl spaces), UL-approved heat tape can provide active warmth.
Crucially, follow manufacturer instructions meticulously to avoid fire
hazards.
Drain Outdoor Lines: Shut off and drain water to outdoor spigots, sprinkler
systems, and swimming pool supply lines before winter hits. Use frost-free
sillcocks if possible.
Strategic Installation: During construction or renovation, advocate for
running PEX pipes through the interior of the building envelope whenever
possible, rather than through cold exterior walls or unventilated crawl
spaces.
What If Your PEX Pipes Freeze?
Locate the Freeze: Check the most vulnerable areas first.
Open the Faucet: Open the faucet supplied by the frozen pipe. This provides
relief for built-up pressure and allows water to flow out once thawing
begins.
Apply Gentle Heat: Never use an open flame or high-heat devices. Use a
hairdryer, heat lamp (kept away from combustibles), or towels soaked in warm
water. Work from the faucet back towards the frozen section. Patience is
key.
Check for Leaks: Once thawed, carefully inspect the pipe and all fittings
for leaks. Pressure can cause failures even after thawing.
Call a Professional: If you can't locate the freeze, can't safely thaw it,
or find a leak, call a licensed plumber immediately.
Conclusion: Vigilance Over Reliance
PEX pipe's flexibility offers a valuable margin of safety compared to rigid
metal pipes if freezing accidentally occurs. However, it absolutely CAN and WILL
freeze if exposed to sub-zero temperatures, and it CAN and WILL burst if the ice
pressure exceeds its limits or if fittings fail. Homeowners should never become
complacent.
The proven strategy for preventing costly water damage is rigorous,
proactive prevention through insulation, sealing drafts, maintaining heat, and
proper installation. Treat PEX with the same caution you would any other
plumbing material when temperatures plummet – because frozen water is an
unstoppable force that demands respect. Protect your pipes, protect your
home.
