In this bulletin we will explore the effects of temperature on PVC pipe.
Polyvinyl Chloride (PVC) is a thermoplastic, and as such, its physical properties change with temperature variations. Dimensions, pressure capacity, and stiffness are all affected by temperature changes. The published dimensions and performance ratings for PVC pipe and conduit products are usually applicable only for 73°F. The following will help to explain how PVC pipe and conduit products are affected by operating temperatures other than 73°F.
Dimensions
Like all materials, PVC expands with increasing temperatures and contracts with decreasing temperatures.
The coefficient of thermal expansion for PVC is:
3.0 x 10-5 in/in/°F
Because the length-to-diameter ratios of PVC pipe and conduit products are generally very large, length change from temperature variation is the most noticeable. A good rule of thumb in design of PVC pipe and conduit systems is to allow 3/8” length variation for every 100 feet of pipe for each 10°F change in temperature. (This rule is independent of pipe size.) Table 1 can also be used to determine the effects of temperature changes on the length of PVC pipe and conduit.
Pressure Capacity PVC pipe exhibits increasing pressure capacity with decreasing temperature, and decreasing pressure capacity with increasing temperature. The pressure ratings given for PVC pipe are for a 73°F operating temperature. To reduce the pressure ratings of PVC pressure pipe for operating temperatures above 73°F, multiply the pressure rating or pressure class by the derating factors in Table 2 on the back of this page.
For applications below 73°F, use the published pressure ratings since they will be conservative.
The maximum recommended operating temperature for PVC pressure pipe is 140°F.
Pipe Stiffness
PVC pipe and conduit becomes stiffer with decreasing temperature and more flexible with increasing temperature. As with dimensions and pressure capacity, published pipe stiffness figures are applicable only for 73°F operating temperatures.
Use Table 3 to reduce the published pipe stiffness of PVC pipe and conduit if the operating temperature exceeds 73°F.
For applications below 73°F, use the published pipe stiffness since they will be conservative.
Table 3 is also applicable as a temperature correction chart for the modulus of elasticity (E) for PVC pipe and conduit.