Thermal Expansion and Contraction As with all thermoplastic piping materials, consideration must be given during the design of the system to the effects of thermal expansion and contraction. The coefficient of linear expansion for Harvel LXT® pipe is 3.89 x 10 –5 in./in./°F. The rate of expansion or contraction can be calculated as follows: ΔL = 12 yL (T) Where: ΔL = amount of expansion or contraction in inches y = 3.89 x 10 –5 L = length of piping run in feet ΔT = temperature change °F (T max. – T @ time of installation or lowest system temperature or maximum system temperature, whichever is greater.)