Compatibility of Sealants with CPVC Pipes and Sprinkler Systems

Chlorinated polyvinyl chloride (CPVC) is an amorphous thermoplastic material. The increased chlorine content compared to standard polyvinyl chloride (PVC) enhances its mechanical performance at elevated temperatures. Consequently, CPVC is commonly utilized in applications such as hot water piping systems and fire sprinkler pipework.

In numerous construction scenarios, it is essential to seal service penetrations (such as pipes, ducts, and cables) in walls and ceilings to prevent the movement of flames, heat, and smoke between neighbouring areas. This is typically accomplished using firestopping materials or intumescent sealants.

It is important to select sealants compatible with the pipe materials used and this is particularly so for safety critical components such as fire sprinkler pipework

The main suppliers of CPVC pipework for fire sprinkler applications maintain lists of approved products that they have tested with their products. However, as the exact formulation of a CPVC compound may vary between suppliers, compatibility of a sealant with one pipe supplier’s product may not necessarily infer compatibility with that of another.

Aside from components of some sealants having the potential to soften and swell the CPVC resulting in a loss of strength, a particular risk of failure comes from environmental stress cracking. 

Common to all amorphous thermoplastics, CPVC is prone to environmental stress cracking (ESC) and common constituents of many sealants such as plasticisers can act as stress cracking agents. 

Contact with an incompatible sealant can lead to crazes forming in the CPVC pipe. During an inspection crazing may not be apparent, as it is typically covered by the sealant.

However, over time, these crazes can coalesce and form a crack which may result in leaking of water and property damage or could to sudden catastrophic failure and the system failing to operate effectively.