Engineering Design

Sanitary Sewer Engineering Design

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 second article is "A More Typical Deflection Response."
Software allows the engineering of any variables that may be experienced on a project and calculates deflection of flexible PVC pipe. Input size, pipe stiffness, depth of cover and live load. This software may be used for any flexible pipe including ductile and fiberglass.

Uni-Bell Software Download Instructions:

Please follow these instructions to download and install the software on your local system. The file size of 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 on your local system.
  3. The 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, click on the button marked “Extract”. You will be prompted for the destination folder to extract the 3 files contained in
  5. After selecting a destination, click “Extract”. The 3 files will be extracted to the destination that you selected.
  6. Exit from the 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.
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.
See the "Urban Myths Die Hard" article for use of PVC gravity sewer applications at depths of 30 feet and more. Many sewer utilities have arbitrarily set depth limits for PVC which are not based on engineering knowledge.
This document has been developed by the Uni-Bell PVC Pipe Association for design and installation of PVC fittings where solid-wall PVC pipe is used in non-pressure applications. The guide provides information on the wide range of fittings that are available for various dimension ratios and outside diameters of PVC pipe through 60-inch. Also included is information on installation practices.
PVC Sanitary 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.
The 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%.
This Uni-Bell Technical Bulletin summarizes recommendations on the installation of risers.
How does ring deflection affect the hydraulic capacity of a buried PVC sewer pipe? Read "The Effects of Deflection on Sewer Hydraulics, The Sequel," from PVC Pipe News.
Uni-Bell's "UNI-B-9-90, Recommended Performance Specifications for Polyvinyl Chloride (PVC) Profile Wall Gravity Sewer Pipe and Fittings Based on Controlled Inside Diameter (Nominal Pipe Sizes 4-48 inches)" covers all the structured wall options available for gravity sewer applications.
This sample specification is offered for those who wish to use PVC in their next project or who would like to add PVC to their standards specifications.