All pipe materials expand and contract with changes in temperature
All pipe materials expand and contract with changes in temperature and this dimensional change must be considered in the design and installation of the piping systems. As a general rule, a 10 degree Fahrenheit change in temperature will cause PVC pipe to expand or contract 3/8″ in for every 100 feet of length. For example, a 1,000 foot pipeline installed in the summer when the ambient temperature is 90 degrees Fahrenheit would shrink about 20 inches if the soil cooled to 40 degrees Fahrenheit in the winter. This change in length must be accommodated or severe damage to the pipe fittings will result.
Source: “Designing, Operating and Maintaining Piping Systems Using PVC Fittings” Ron Bliesner, February 3, 1987