CONTECH Written

Written

Course Information
Buried flexible sewer pipes come in a variety of materials. The most common in the United States are corrugated metal (CMP), polyvinyl chloride (PVC), centrifugally cast glass-fiber-reinforced polymer mortar (CCFRPM or fiberglass), solid wall polyethylene (PE), steel reinforced polyethylene (SRPE), corrugated PE and polypropylene (PP) pipe. Design engineers often seek simple ways to compare between all of these different materials. It is easy to categorize the various materials by use of simple acronyms such as CMP, HDPE, PVC, etc.

For hydraulics, the Manning’s (n) value is utilized. For joint tightness, referencing the requirements of ASTM D3212’s 10.8 psi water tightness is the most common. In pressure applications, there are pressure ratings. It is more difficult, however, to find a simplistic way to quantitatively compare structural performance or pipe strength. One of the most common ways to attempt to compare structural performance is the use of pipe stiffness.

Author
Andrew Jenkins and Darrell Sanders, P.E.

Learning Objectives
At the conclusion of this article, the reader should be able to understand:

• The basics of flexible pipe stiffness

• How using pipe stiffness can result in false equivalency performance expectations

• Examples of differences in performance of pipe types with similar pipe stiffness