Design & Installation

Thermal Expansion and Contraction

Like all piping material, FlowGuard Gold® CPVC and Corzan® CPVC expand when heated and contract when cooled. CPVC piping (regardless of pipe diameter) will expand about 1 inch per 50 feet of length when subjected to a 50°F temperature increase. Therefore, allowances must be made for this resulting movement. However, laboratory testing and installation experience have demonstrated that the practical issues are much smaller than the coefficient of thermal expansion would suggest. The stresses developed in CPVC pipe are generally much smaller than those developed in metal pipe for equal temperature changes because of the difference in elastic modulus. Required loops are smaller than those recommended by the Copper Development Association for copper systems.

Expansion is mainly a concern in hot water lines. Generally, thermal expansion can be accommodated with changes in direction; however, a long straight run may require an offset or loop. Only one expansion loop, properly sized, is required in any single straight run, regardless of its total length. If more convenient, two or more smaller expansion loops, properly sized, can be utilized in a single run of pipe to accommodate the thermal movement. Be sure to hang pipe with smooth straps that will not restrict movement.

For above ground installations, be sure to hang pipe with smooth straps that will not restrict movement.

For under slab or below ground installations, be sure backfill material will not restrict movement at the expansion loop, offset or change of direction.

For convenience, loop (or offset) lengths have been calculated for different pipe sizes and different run lengths with a temperature increase (T) of about 80°F. The results, shown in Tables 18 and 19, are presented simply as a handy guide for quick and easy determinations of acceptable loop lengths for the approximate conditions. Loop length for other temperatures and run lengths can be calculated utilizing the following equations: