What is the difference between pressure class and pressure rating?
The three most common PVC pressure pipe products manufactured by Uni-Bell member companies are ASTM D2241, AWWA C900 and AWWA C905. The following information will briefly explain the differences between the Pressure Class and Pressure Rating design philosophies employed in these three standards. AWWA C900 has a Pressure Class design approach based on a 2.0 safety factor. AWWA C900 is intended for use inside the looped perimeter of an urban water system where piping system geometry is complex. Surge pressures should be accounted for in the design. AWWA C905 has a Pressure Rating design approach based on the 2.0 safety factor. AWWA C905 is intended for use as water transmission piping where long straight runs are the norm and system geometry is more simplistic. As for C900, surge pressures should be accounted for in design. ASTM D2241 has a Pressure Rating design approach based on the 2.0 safety factor. Once again, surge calculations are the designers responsibility.
