Is thermal expansion and contraction of HDPE pipe a problem?

No. All pipes expand and contract with change in temperature. The key is management of the resultant thermal strain. As with all materials, expansion and contraction must be taken into consideration when designing a HDPE piping system. Buried pipelines usually do not move due to soil friction. However, thermal effects must be considered for above grade applications. The unrestrained coefficient of thermal expansion for HDPE pipe is approximately 9x10-5 in/in/oF. Information regarding thermal calculations for restrained and unrestrained above-ground and slip-lined pipelines can be found in PPI’s Handbook of Polyethylene Pipe, 2nd ed.