Every PEX manufacturer supplies fittings to go with its
tubing. Naturally, if you’re using a company’s
tubing, they want you to use their fittings, too — no
company recommends mixing brands of tubing and fittings.
The different methods of making joints vary quite a bit.
Wirsbo’s basic joint for residential plumbing is a simple
expansion joint, based on the tubing’s "memory," or
tendency to return to its original shape whenever it’s
deformed. To make the joint, you expand the tube with a special
Wirsbo insert tool and quickly slide the expanded tube over the
nipple of the fitting. In a split second, the tube shrinks and
grabs the fitting (Figure 3).
3. To make a simple joint using Wirsbo's method, you
slide a PEX ring over the tube, expand the tube with Wirsbo's
expanding tool (left), and quickly insert the fitting (right)
before the PEX returns to its original diameter.
You have to move fast to slip in the fitting, and once the
joint’s together, you can’t pull it apart. For
added strength, you slip a second ring of PEX over the tube
before expanding it. After 30 minutes, the joint can be
pressure-tested to 200 psi.
I prefer the crimp fittings supplied by Vanguard, because
they’re easier to use. With this fitting, the tube
doesn’t have to be expanded: The male end of the fitting
slides into the tube easily. You use a special crimping tool
supplied by Vanguard to crimp a copper ring over the joint
4. In the Vanguard joint system, tubing slides over the
fitting without expanding (left) and is secured with a copper
crimp ring. Crimping with Vanguard’s crimping tool takes
only a few seconds (right).
Unlike the expansion joints, which are permanent right away,
crimp joints can be pulled apart until the ring is actually
crimped. This allows us to make a temporary joint at the end of
a line, using a fitting that doesn’t belong there, until
we come back with the correct part. However, you can get in
trouble leaving joints assembled but uncrimped. Sometimes it
seems quicker to make a bunch of joints, then go back and crimp
them all at once. But you’d better not forget one, or
you’ll have a leak.
Vanguard supplies a go/no-go gauge for checking joints to
make sure they’re properly crimped. If the gauge slips
over the ring, it’s a go. But Vanguard’s new crimp
rings also have a black coating that gets scraped off when the
ring is crimped — if the ring’s still black, you
know it hasn’t been crimped. However, you still have to
routinely check the crimped joints with the gauge to make sure
your crimping tool is properly calibrated.
A third type of joint, which uses a compression fitting,
comes as standard issue on manifolds (and the valves I use in
making my own manifolds). To make these joints, you simply
slide the tubing over the nipple, then tighten down a locknut
that pushes a compression ring over the tubing. Depending on
the tube’s inside diameter and the fitting size, you may
have to expand the tube first. When these joints are only
finger-tight, they can be backed out; but once you tighten them
with a wrench, they’ll never come loose. For added
security, though, we use a thread lock like Loctite to make
sure the nuts don’t work off.
The mother of all joints is a compression-ring fitting
system supplied by Rehau. To make those connections, you expand
the tube and slip it over the fitting, then use a foot-operated
hydraulic press to force a heavy-duty brass ring over the tube
and fitting (Figure 5).
5. Rehau’s joint method uses a
foot-operated hydraulic press to force a heavy-duty
brass ring over the tube and fitting. The author rarely
uses these heavy-duty joints in residential