Law Supply, Inc.
Web Page - Lineal Thermal Expansion Curve For PVC Pipe
The values for this curve are based on a ten (10) foot section of pipe,  Values for larger spans can be obtained by multiplying the values form this curve by the span length (in feet) and divided by ten.
This curve is based on the equation
Expansion and Contraction During Installation
Pipe coupled-up ditch side in hot sun expands appreciably, and pipe surface temperatures may be 120°F.  When the pie is filled with water for testing or service, the temperature may drop to 70°F.  This 50°F temperature change would cause a contraction of 1.8 inches per 100 feet of PVC-1 (form chart), and would cause coupling leads or failures if not controlled.
This contraction is normally handled by snaking the pipe from side to side in the ditch during installation, and covering with 2 or 3 inches of loose fill as the installation progresses to prevent excessive surface temperature buildup on the pipe.  The joints are left exposed for subsequent testing for leads.  When the line is slowly filled with water for testing and air expulsion, the temperature change, and resultant contraction, is easily handled by the additional length in the snaked section.

Expansion and Contraction in Service
After the earth in a trench is well settled or heavily compacted, the buried line is relatively immobilized and the snaked line offers very little expansion and contraction control.
Where ambient ground and fluid temperatures are nearly equal and relatively constant, the expansion and contraction changes are absorbed in the pipe walls and slight linear movements in the line.
However, in exposed lines or in buried lines where ambient or ground temperatures differ appreciably, expansion and contraction joints must be installed in the line at properly spaced intervals to provide control.



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 Last updated 03/31/2003
Information taken from CANTEX Manual