Technical Blog

Welcome to John’s Blog. Answers to frequently asked questions are periodically posted here. The objective is to share information about PVC pipe with readers as well as with utilities, design engineers and pipe installers. The blog provides the latest information on PVC pipe design, installation, and application for water and wastewater infrastructure projects.

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John Houle: Senior Technical Consultant, PVC Pipe Industry

John Houle holds a Master’s Degree in Civil Engineering from the University of Missouri and an MBA from the University of Oregon. He has more than 25 years of experience in the plastic pipe industry in applications engineering, market development, forensic analysis, technical writing, and standards development.

Correct Assembly of Gasketed PVC Pipe Maximizes Joint Performance

Posted By John Houle on Mar 27, 2013

Gasketed PVC Pipe: The Importance of Insertion Lines

Many pipe installers think that a PVC pipe spigot is correctly installed if its insertion line has disappeared into the pipe bell. They believe that the purpose of the line is to ensure that the spigot has been installed far enough to allow the gasket to seal properly. This is only partly correct.

The first purpose is to ensure that the gasket will properly engage with the spigot to form a leak-free joint. If there is a space between the line and the bell, sealing may be affected.
The second reason is to prevent the spigot from being inserted too far into the bell. If the line is not visible, the spigot has been over-inserted.

Thus, the insertion line is barely visible in properly installed PVC pipe. As the technical brief, “Gasketed PVC Pipe: The Importance of Insertion Lines,” explains (click here), there is more than one purpose for the insertion line. Over-insertion is not ideal because it defeats some of the benefits of PVC pipe joint design.

Expansion Gaps for Gasketed PVC Pipe: Maximizing Joint Performance

With correct installation, there is a horizontal gap inside the joint between the end of the spigot and the shoulder of the bell. The gap occurs in both pressure and non-pressure pipe, but is observable only during video inspection of gravity-flow sanitary sewer pipe. The gap is necessary to provide room for thermal expansion of the pipe and to allow for angular joint deflection that accommodates any ground movement that occurs. The gap is an integral feature of the joint design and does not affect the joint’s water-tightness or its hydraulic characteristics.

Click here to read the technical brief, “Expansion Gaps for Gasketed PVC Pipe: Maximizing Joint Performance.”

More than sixty years of experience have shown that PVC pipe joints function reliably long-term even when not installed perfectly. However, the recommendations of these technical briefs should be followed to maximize joint performance.