Why Do PVC & CPVC Pipes Occasionally Fail

PVC and CPVC pipes and fittings are excellent products and have been used successfully for decades.

There is a low failure rate and the use of PVC/CPVC materials offer significant advantages over metal piping materials including ease of installation and very low failure rates.

However, as with all plumbing products including metal piping, occasionally a pipe or fitting may fail. When a failure does occur, our experience indicates that often the failure can be linked to improper installation practices, which is why it is imperative that you hire a qualified contractor. Searching for plumbers who can successfully undertake this work can be quite complicated too.

The intent of this article is to provide assistance regarding installation errors to avoid and thereby reduce the occurrence of a failure in PVC and CPVC plumbing.

Again, let me emphasize that by teaching about the main causes of occasional failure of PVC and CPVC pipes and fittings, I am in no way suggesting that these plumbing products are less reliable or more prone to failure than any other plumbing material.

Most of the Main Causes of CPVC/PVC Pipe Failures are briefly detailed Below:

Improper System Engineering/Installation

A. Inadequate provision for linear thermal expansion.
B. Excess use of Cement.
C. Insufficient amount of Cement.
D. Wrong Clamps used or Clamps too tight.
E. Incompatible fire caulk used.
F. Contact of outside of pipe with incompatible material (e.g., solder flux).

Improper Operation

A. Exposure to freezing temperatures without freeze protection.
B. Over-pressurization.
C. Pulsating water pressure.
D. Use of incompatible materials around pipes.


A. Internal
1. Use of contaminated antifreeze.
2. Contaminants from metal water supply piping; e.g., antimicrobial (MIC inhibitor) linings, corrosion inhibitors, phthalate plasticizers from pump seals/gaskets, refrigeration system lubricants.

B. External
1. Incompatible Fire Caulk.
2. Use of incompatible (black Proset) grommets to seal pipe against hole in concrete.
3. Contact with incompatible plastic coated wires.
4. Exposure to hot solder flux.
5. Exposure to hot polyurethane foam insulation.

Manufacturing defects

A. Dirty extrusion die.
B. Incomplete resin consolidation.
C. High stresses in pipe wall due to rapid cooling.

Resin Defects

A. Occlusions, char particles, voids.
B. Filler/pigment not well distributed.

Abuse by the Distributor

A. Store in sun.
B. Damage during transport.

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