Like other flexible pipe materials, PVC experiences ring deflection in response to external loads. Two PVC Pipe News articles review the deflection-response mechanism. The first article is "Back to Basics: Time Dependent Variables for Flexible Sewer Pipe." The article reviews the key elements that determine the long-term ring deflection that a flexible pipe will experience. It will also show that the time-dependent elements do not include creep. The second article is "A More Typical Deflection Response."

Clicking the download button brings up the menu for Uni-Bell's design software, "External Load Design for Flexible Conduits." The software doesn't apply exclusively to PVC. It may be used for calculating the long-term deflections of any flexible pipe material.

Uni-Bell Software Download Instructions:

Please follow these instructions to download and install the software on your local system. The file size of UniBell_LoadDesign.zip is 2.2 MB. Estimated time to download with a 56k modem is 2 minutes.

1. Complete the download to a folder you can access on your local system.
2. After completion of the download, locate the file UniBell_LoadDesign.zip on your local system.
3. The UniBell_LoadDesign.zip file is a zip file. Upon double-clicking the file, it will open to show 3 individual files. You may want to move the file to an individual folder before extracting the files.
4. After double-clicking on the UniBell_LoadDesign.zip, click on the button marked “Extract”. You will be prompted for the destination folder to extract the 3 files contained in UniBell_LoadDesign.zip.
5. After selecting a destination, click “Extract”. The 3 files will be extracted to the destination that you selected.
6. Exit from the UniBell_LoadDesign.zip file.
7. Locate the files extracted on your local drive using Windows Explorer.
8. Double-click on setup.exe to start the installation of the software on your local system.
9. Click ok, then click on the computer icon and click on ok.

This Uni-Bell Technical Report, "UNI-TR-1, Deflection: The Pipe/Soil Mechanism," details design procedures for predicting the long-term deflection of buried PVC pipe.

PVC Sewer Pipe Standards are summarized on a single sheet.

This Canada-specific comparison of PVC and polypropylene (PP) sewer pipes is based on: (1) For PVC sewer pipe – decades of research and field experience: (2) For PP’s new sanitary-sewer pipe – brief history of usage with unknown longevity.

ASTM standards limit ring deflection to 7.5%. The PVC Pipe News article, "Deflection: What Are the Limits?" looks at performance issues when ring deflection exceeds 7.5%.

How does ring deflection affect the hydraulic capacity of buried PVC sewer pipe? Read "The Effects of Deflection on Sewer Hydraulics, The Sequel," from PVC Pipe News.

Article and photo demonstrate how flexible PVC can be used in shallow bury applications.