and work backward along the run to establish
bends and secure the tube to the frame of the
building. When at the point where the next
fitting is to be installed, cut the tube and install
the fitting. This greatly reduces the need to use
a rule.
Making Bends in PEX
A major concern when bending PEX is how
small of a radius it can bend without causing
the inside of the tube to begin closing. The rule
of thumb is that the bend should not be smaller
than 8 times the actual outside diameter of the
tube, Figure 20-23.
Special bend supports, Figure 20-24, are
available to hold the tube in the correct radius
bend. The bend support also eliminates much
of the pressure that would otherwise be placed
on the fitting by the tube’s natural tendency to
straighten. If a smaller radius bend is required,
an ell must be installed. Larger radius bends
can be secured with straps near each end of
the bend.
Cutting and Joining PEX
1. Cut the PEX tube to the desired length. A
tube cutter makes achieving a square cut on
PEX tube very easy. See Figure 20-25.
2. Once the tube is cut, a crimp ring is slipped
onto the tube.
3. Insert the fitting inside the tube
4. Use the crimping tool to secure the crimp
ring.
5. Check every crimp ring with a crimp gauge to
determine if it has been sufficiently crimped.
If the gauge will not slip over the ring, the ring
and fitting must be removed and new ones
installed. Recrimping does not work.
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Section 3 Plumbing System Design and Installation
PEX was developed in the late 1950s by
scientists working on the molecular structure
of polyvinyl chloride to produce a more heat
resistant product. Three different manufactur-
ing processes have been developed for PEX.
All three produce materials that are approved
for plumbing.
History Brief
Figure 20-23. Bends in PEX tube should not be smaller
than shown in this table.
Bend radius
Tube Size Bend Radius
1⁄2 5″
3⁄4 7″
1 9″
Figure 20-24. Bend supports maintain the correct
bend radius and relieve stress on fittings.