PEX-al-PEX, a composite pipe combining the flexibility of PEX with an
aluminum core, was once hailed as a revolutionary plumbing material. But with
evolving building codes and new materials emerging, many wonder: is PEX-al-PEX
still used today? The short answer is yes, but its application has become more
specialized and region-dependent.
This article explores the current status of PEX-al-PEX, its advantages,
limitations, and where it still fits in modern plumbing and heating systems.
What is PEX-al-PEX?
PEX-al-PEX (or PEX/Aluminum/PEX) is a multilayer pipe. It consists of an
inner layer of cross-linked polyethylene (PEX), a middle layer of welded
aluminum, and an outer layer of PEX. The aluminum core provides rigidity, oxygen
diffusion barrier properties, and shape memory (allowing the pipe to hold
bends), while the PEX layers offer corrosion resistance and flexibility.
Current Usage and Market Position
While pure PEX pipes (PEX-a, PEX-b, PEX-c) now dominate the residential
plumbing market in regions like North America, PEX-al-PEX maintains a presence
in specific applications:
Radiant Floor Heating Systems: This remains a stronghold for PEX-al-PEX.
The aluminum layer acts as an excellent oxygen barrier, preventing corrosion of
ferrous components (like boilers and circulators) in closed-loop heating
systems. Its shape memory also makes neat, uniform installation easier over
large subfloor areas.
Commercial Plumbing and HVAC: In commercial buildings, where longer
straight runs and higher rigidity are often required, the aluminum's stiffness
can be advantageous, reducing the number of required clips or supports.
European and Specific Regional Markets: Its use is more prevalent in Europe
and parts of Asia, where building traditions and codes have historically favored
multilayer composite pipes for both plumbing and heating.
Retrofit Projects: Its ability to hold a bend with less springback can be
beneficial in tricky retrofit situations where precise maneuvering is
needed.
Key Advantages: Why It's Still Specified
Superior Oxygen Barrier: Crucial for protecting heating system
longevity.
Low Thermal Expansion: Expands less than pure PEX when heated, which can
reduce stress on fittings.
Dimensional Stability and Stiffness: Holds its shape well for neat
installations.
Good Gas Barrier: Prevents diffusion of other gases, potentially relevant
for certain applications.
Challenges and Reasons for Niche Use
Cost: It is significantly more expensive than standard PEX pipes.
Complex Installation: Requires specific ring crimp or compression tools,
and the aluminum layer can make it less forgiving during bending if not done
correctly (risk of kinking).
Not Required for Most Plumbing: For domestic cold and hot water supply, the
oxygen barrier is unnecessary. Standard PEX is cheaper, more flexible, and
easier to install, meeting all code requirements.
Competition from EVOH-barrier PEX: Many PEX manufacturers now offer pipes
with an ethylene vinyl alcohol (EVOH) oxygen diffusion barrier as a coextruded
layer. This provides adequate protection for most residential heating systems at
a lower cost and with standard PEX installation methods.
