PEX stands for cross-linked polyethylene, (and is sometimes referred to as
XLPE.) Polyethylene is composed of chains of ethylene molecules referred to as
polymers, (hence “poly”-ethylene.) These polymers don’t connect, which is what
gives polyethylene its flexibility. It's produced in two main forms, low density
(LDPE) and high density (HDPE). In HDPE, the polymers are tightly packed, which
makes it stiffer than LDPE. HDPE is used in common items such as milk bottles
and LDPE is used in film applications, such as food wraps or trash bags.
HDPE, in general, has good impact resistance. When crosslinked by any of the
methods, A, B or C the HDPE overcomes some of its natural material properties,
making the finished product more resilient for potable and radiant applications.
Always check the markings on the pipe, called the print-line, for corresponding
fastening methods and ratings for temperature and pressure.
Note: PEX comes in types A, B, and C. Only PEX A can be used
with the expansion connection system.
PEX Pipe Advantages
There are many benefits of PEX piping, including:
Lower cost to install. PEX costs roughly the third of the price that
copper piping costs.
Corrosion resistance. Unlike galvanized steel pipes and copper piping,
PEX is resistant to corrosion, mineral buildup, and erosion.
Ease of installation. For many minor DIY projects, it doesn’t require a
plumbing license to do your own PEX pipe installation (although there are
special tools). For example, one can replace old pipes in a leaky sink.
Since PEX is flexible, it allows for easy installation in hard to reach
places. Efficiency. PEX pipes have a smaller diameter than other types of
pipes, so the wait for hot water is shorter, resulting in less waste of
water. Additionally, PEX material has greater thermal conductivity
properties than other types of pipes which reduces heat loss.
Quiet operation. You won’t have to worry about pipes rattling with PEX
since they made out of synthetic plastic.
PEX Pipe Disadvantages
Installation errors. While some people may find PEX installation to be
easy, others may be in over their heads. We recommend leaving pipe
installation up to the professionals, especially if it involves more moving
parts, running lines from other rooms, or in brand new construction.
Heat damage. PEX is susceptible to failure in high-heat situations so it
cannot be installed directly to water heaters (although there are connection
materials to workaround). It also cannot be placed near recessed lighting.
UV light. PEX is very sensitive to UV light, so it’s important that all
PEX piping be hidden from direct sunlight and UV lightbulbs. Many
manufacturers recommend total darkness for PEX pipes so this limits where it
can be installed.
Chemical issues. Some types of PEX have been known to leach toxic
chemicals like BPA and other contaminants. PEX can also be damaged due to
high levels of chlorine in the water. Always have your water tested before
PEX installation to see if it’s suitable to use.
Permeability. Since PEX is plastic, there’s a likelihood of damage, and
rodents can even chew through the pipes. PEX is not suited for outdoor
installation or exposure to elements. PEX is permeable which means liquids
can enter the pipe.
