PVC Expansion and How to Deal with it

"For want of a nail the shoe was lost,
for want of a shoe the horse was lost;
and for want of a horse the rider was lost;
being overtaken and slain by the enemy,
all for want of care about a horse-shoe nail."

— Benjamin Franklin

Introduction

Figure 1: PVC Pipe.

Figure 1: PVC Pipe.

I have written a post about the problems that I encounter with the improper use of PVC pipes and accessories in outdoor Fiber-To-The-Home (FTTH) deployments. During my normal reading about codes and regulations, I found an example of a bad installation and an example of how to properly deal with PVC expansion by installing an expansion joint. Both of these items deserve some coverage here.

Example of a Bad Installation

Figure 2 is from EC&M magazine and shows two problems:

  • Indoor-rated PVC pipe holding clips were used outdoors.
    Constant UV exposure weakened the clips and they dropped the pipe.
  • Temperature variation eventually caused the pipe to separate from its joint.
    I am not sure if this joint was glued, but I have seen pipes expand/contract so much that they break a glued joint. This joint might not have been glued and it just pulled apart.
Figure 1: Example of Bad PVC Installation.

Figure 2: Example of Bad PVC Installation.

Example of an Expansion Joint

The standard way to deal with this problem is to install an expansion joint. The video below shows an example of a good installation.

Conclusion

A little bit of extra time on this installation would have prevented a call-back.

 
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