Installation Guide

54
Plastics Technical Manual
Support Spacing For ABS and
PVC Pipe
Adequate support for any piping system is a matter of great
importance. In practice, support spacings are a function of pipe
size,operatingtemperatures,thelocationofheavyvalvesor
fittings, and the mechanical properties of the pipe material.
To ensurethesatisfactory operationofaDWVorpressure
piping system, the location and type of hangers should be
carefully considered. The principles of design for metallic
piping systems are generally also applicable to DWV or
pressure piping systems, but with some notable areas where
specialconsiderationshouldbeexercised.Hangersshouldnot
compress, distort, cut or abrade the piping.
All piping should be supported with an approved hanger at
intervals sufficiently close to maintain correct pipe alignment
and to prevent sagging or grade reversal. Pipe should also be
supported at all branch ends and at all changes of direction.
Support trap arms as close as possible to the trap. In keeping
with good plumbing practices, support and brace all closet
bends and fasten closet flanges.
(1) Concentrated loads (ie: Valves and other appurtenances)
should be supported directly so as to eliminate high stress
con centrations. Should this be impractical, then the pipe
must be supported immediately adjacent to the load.
(2) In systems where large fluctuations in temperature occur,
allowances must be made for expansion and contraction
of the piping system. Since changes in direction in the
system are usually sufficient to allow for expansion and
contraction, hangers must be placed so as not to restrict
this movement.
(3) Since plastic pipe expands or contracts approximately
five times more than steel, hangers should not restrict this
movement.Whenusingaclamp-typehanger,thehanger
should not force the pipe and fittings into position.
(4) Hangers should provide as much bearing surface as
possible. To prevent damage to the pipe, file smooth any
sharp edges or burrs on the hangers or supports.
(5) Plastic piping systems must not be placed alongside
steam or other high temperature pipe lines or other high
temperature objects.
(6) Supportspacing for horizontal pipingsystemsmustbe
determined by the maximum operating temperature the
system will encounter. The piping should be supported
on uniform centers with supports that do not restrict the
axial movement.
(7) For vertical lines, it is recommended that an engineer
design the vertical supports according to the vertical load
involved.
(8) Changes in direction should be supported as close as
practical to the fitting to avoid introducing excessive
torsional stresses into the system. Please see the
associated chart showing the recommended support
spacing according to size, schedule, and operating
temperatures. These spacings apply to continuous spans
of uninsulated lines, with no concentrated loads, conveying
liquids with specific gravities of up to 1.00.
Horizontal and Vertical Support
for CPVC Pipe
Mostplumbingcodesandbuildingcodesrequiresupportfor
horizontalpipelinesevery3feetforpipein1/2”-1”diameters,
and every 4 feet for pipe with diameters greater than 1”.
Support spacing should be in accordance with applicable
plumbing and building codes.
Vertical CPVC piping should be properly supported and have
a mid-story guide, unless thermal expansion requires another
design.
The pipe should not be anchored tightly by the support, but
secured in a manner to allow for movement caused by thermal
expansion and contraction. It is recommended that you use
clamps or straps that allow pipe to remain away from the
framing, thus reducing the noise generated when pipe is
allowedtorubagainstwood.Usehangersandclampsthat
are chemically compatible with CPVC.
Plastic insulators do not need to be used when CPVC pipe
passesthroughwoodstuds.However,whenCPVCpipepasses
through metal studs, some forms of protection must be used
to isolate the pipe from abrasion and to prevent noise.
NOTICE: The above information on this page provides general
guidelines. It should be used only as a reference and not as a
guarantee of performance. Specific installation instructions
and techniques may be required as a result of local plumbing
and building codes, engineering specifications and instructions.
DESIGN & ENGINEERING DATA
Failure to compensate for expansion and contraction
caused by temperature change may result in system
failure and property damage.
• Do not restrict expansion or contraction. Restraining
movement in piping systems is not recommended and
may result in joint or fitting failure.
• Use straps or clamps that allow for piping system
movement.
• Align all piping system components properly without
strain. Do not bend or pull pipe into position after being
solvent welded.
• Do not terminate a pipe run against a stationary object
(example: wall or floor joist).
• Do not install fittings under stress.