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Cross-linked Polyethylene (PEX) has been used since the
80's. Originally used in Europe, it is now very popular in the United
States. Home inspectors often see PEX improperly installed. We know
that PEX manufacturers normally want installers to use a manifold
system with “home runs” to the individual fixtures. Multiple elbows and
“T” connections are not ordinarily recommended. A past newsletter
specifically details PEX installation procedures. You can find a great
PEX installation manual by CLICKING
HERE.
Recently there have been at least two lawsuits
pertaining to PEX installation. There was also a recent case where
Uponor reached a $18 Million class action settlement. This settlement
deals with fitting issues. More information can be found on the “News
from the Home Inspector World” & "New Products" links in
the right pane of this newsletter.
So what are some of the alleged problems associated with
PEX installation? Some brass fittings may fail due to dezincification.
This may occur when zinc leaches from the fittings. It will create a
white powder substance from the breakdown and possibly reduced water
flow. It may also cause leaks in the fitting (see photo above).
High levels of chlorine have been known to oxidize the
inner wall of some types of pipe causing the connections to fail. We
saw this problem with Polybutylene pipe. Some manufactures have added
antioxidants to the pipe for sacrificial purposes. The chlorine will
degrade the antioxidants before the pipe. It is not known the long term
effect of chlorine and pipe failure. The amount of chlorine used in
Europe is significantly lower than the U.S. A higher level of chlorine
may cause accelerated degradation.
Some types of plastic pipe are manufactured in a manner
where chemical leaching may occur. This involves leaving chemical
byproducts behind in the pipe. Buried pipe may also be permeable when
exposed to some solutions including oxygen, petroleum products, and
chemicals. This may cause toxic chemicals to leach from the pipe
material.
Many PEX manufactures have addressed potential issues
and have also introduced different grades of PEX for specific uses. For
instance:
·
Non-Oxygen Barrier
PEX for potable water
·
Oxygen Barrier PEX
for heating system components that may rust or corrode
·
PEX – A -
flexible, less kink resistant, & freeze resistant
·
PEX – B – slightly
less flexible and not as freeze resistant as PEX-A
·
PEX-AL-PEX or
Aluminum Barrier PEX – impregnated with a layer of aluminum, it keeps
it shape when bent. The aluminum also is an oxygen barrier and has a
low expansion rate. This is used for outdoor or high temperature
heating systems.
What should a home inspector be looking for (especially
in older PEX):
Proper installation (refer to past newsletter or the
PEX installation manual)
White powder around PEX fittings (see photos at the
beginning of article)
Visible leaks or “weeping” especially at the
fittings
Reduced water flow at the fixtures
PEX should not be exposed to sunlight, even through
windows
PEX should be protected from potential nail or screw
pierce
Odor or bad taste of the water
It is currently uncertain how any of these potential
conditions may effect plumbing pipe manufacturing and it's expected
serviceable life.
Of course, improper installation will also cause
failure. Reviewing the installation manual will help you understand
what to look for when inspecting PEX pipe.
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