Why Are My CPVC Pipes Melting?

History

• CPVC pipes have been used in water distribution systems since 1959, according to the Plastic Pipe and Fittings Association. Many CPVC pipes installed since then are still performing with minimal required repairs. CPVC is not only sturdy, but is less costly because of the low-cost tools needed for installation and lower manufacturing cost.

Welding

• CPVC and PVC pipes are installed and welded using chemicals. Unlike metal pipes that sometimes require welding using a blow torch and a variety of professional tools for tightly securing the pipes and fittings, CPVC and PVC require two chemicals: a primer ensuring dirt, oil and grease are removed, and solvent cement bonding the pipes and fitting together. Both the primer and solvent slightly soften the fixtures. The pipes then create a bond because of the cement solvent applied.

Installation

• When the CPVC pipes are connected, primer is applied and then the cement solvent. Although the same primer can be applied to CPVC and PVC pipes, different solvent cements are used on each type of pipe. The cement solvents are designed to react to the chemical compounds used in creating each type of plastic pipe. Using a PVC cement solvent on a CPVC pipe can cause a chemical reaction, resulting in the pipes melting. Because both the primer and solvent cement are used to make the pipes more flexible, if the products are overused or not removed from other areas of the pipe other than the fittings, it could melt the pipe.

Solution

• If CPVC pipes are melting, replace them. Unlike metal pipes, CPVC pipes can be easily repaired and replaced. Cut out the joint where the pipe melted with a handsaw. Use CPVC expansion repair joint to replace the melted joint. Use primer recommended by the manufacturer of the CPVC expansion joint. Only use CPVC solvent cement to weld the repair area.