Compatibility of Sealants with CPVC Pipes and Sprinkler Systems

CPVC is an amorphous thermoplastic material. The additional chlorine content relative to a standard PVC material produces improved elevated temperature mechanical; performance and amongst other applications the material find uses in hot water pipe systems and fire sprinkler pipework.

In many building applications there is a requirement for service penetrations (pipes, ducts and cables) through walls and ceilings to be sealed to contain the spread of flame, heat and smoke between adjacent compartments. This is commonly achieved by the use of firestopping or intumescent sealants.

Cracked CPVC fire sprinkler pipe after contact with incompatible intumescent sealant.

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. 

 Crack in CPVC sprinkler caused by incompatible sealant
Crack in CPVC sprinkler caused by incompatible sealant 

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. 

If a specific sealant product is to be used in contact with CPVC pipework and it is not approved for use by the pipe manufacturer we strongly recommend an assessment is made to confirm compatibility before the pipe system is installed. 

At ipolytech we have assessed failed pipework from numerous installations, compared the composition of sealants removed from site with reference samples and developed test procedures for assessing the compatibility of intumescent sealants with CPVC material

Crazed edge of CPVC test piece after exposure to incompatible sealant.
Crazed edge of CPVC test piece after exposure to incompatible sealant.