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Correct Assembly of Gasketed PVC Pipe Maximizes Joint Performance

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.

  1. 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.
  2. 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 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.

Link to PVC Pipe Association


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.

Read the technical brief, Expansion Gaps for Gasketed PVC Pipe: Maximizing Joint Performance.

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.

Link to PVC Pipe Association

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