What Is PEX?
Through the
manufacturing process, links between polyethylene molecules are
formed to create bridges, thus giving it the name "crossed
linked". This tubing is especially good in hot water
applications. Because of its design, PEX is more durable under
temperature extremes and chemical attack, and is more resistant
to creep deformation. PEX was developed in the 1960s, and was
used mainly in Europe until the 1980s.
Installing PEX
There are many
different applications for PEX installations; here we will focus
on the installation for a hot and cold water distribution
system.
PEX Fittings
PEX tubing designed for the job
Tubing cutter
Ring crimper
Crimp rings
"Go/No-Go" gauge
Crimp ring removal tool
When cutting PEX, it is imperative that it is a straight, burr
free cut. Measure out the length of PEX you will need for
installation and cut it with the PEX tubing cutter. These pliers
are especially designed for PEX and should always be used.
When you have the PEX cut to length, slip a copper crimp ring
onto the PEX pipe.
Insert the tubing into the piper fitting. It should bottom out
on the shoulder of the PEX fitting. Slide the copper crimp ring up
so that it is 1/8" to 1/4" away from the PEX tubing.
Crimp the copper crimp ring with the ring crimper, insuring that
the PEX crimper is at a 90 degrees angle from the crimp ring. Close
the crimp tool fully on the crimp ring.
Now, test the crimp with the Go/No-Go gauge. The Go-gauge should
slide onto the PEX fitting with ease. It may be tight where the
crimping tool has marked the crimping surface during the
crimping operation. The No-Go gauge must not slide over the
fitting. If it does, the PEX tubing must be recut and the joint made
once again.
Inspect Your
Work
A bit of finesse
is required here. It is very important that the finished PEX joint
is done correctly. Here is what to look for:
Ring crimped over the end of the PEX tubing. Not enough ribs
covered.
PEX crimp tool not at 90 degrees. Plastic dented and not enough rib
coverage.
Copper crimp ring not completely covered by PEX crimping tool. Ring
is distorted with a non uniform crimp.
PEX tubing not squarely cut. Does not cover ribs of fitting.
All of these will cause a potential leak hazard and an
insufficient connection. The crimp tool is designed to make
accurate PEX crimps. It may need adjustment if you continually make
improper connections.
Running The
PEX Tubing
PEX will install a
bit differently than normal PVC or copper tubing. Allowances
must be made for ever 10 degrees of change in temperature. PEX
will contract one inch every 100 feet of pipe with every 10° of
temperature change. Offset this by making a loop in the PEX that
is no more than 8 times the diameter of the PEX tubing.
You will need straps and hangers when installing the PEX. It
must be supported at least every 32 inches if PEX tubing is
installed alongside a joist. If it is placed atop a beam, it
should be supported every 6 feet. When run vertically, it will
require support at every floor level. When installing, always
leave slack in the PEX tubing to allow for contraction. The support
hangers should not be so tight that they will restrict movement
of the PEX.
by Alden Smith |
