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CROSS Safety Report

Non approved sealants are used with CPVC pipes and fittings

Report ID: 1228 Published: 20 February 2024 Region: CROSS-UK


A reporter highlights a concern when non approved sealants are used with chlorinated polyvinyl chloride (CPVC) sprinkler system pipework and fittings. This can cause failures and/or leaks.

Key Learning Outcomes

For sprinkler system designers, specifiers, installers, and maintainers:

  • Installers of critical fire safety installations such as sprinklers must be competent. It is critical that installers:

    • Study the pipe supplier literature carefully
    • Only use sealants approved by CPVC pipe suppliers 
  • Anyone who commissions, installs, or maintains a CPVC sprinkler system should check that the approved sealants have been used

Full Report

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The Full Report below has been submitted to CROSS and describes the reporter’s experience. The text has been edited for clarity and to ensure anonymity and confidentiality by removing any identifiable details. If you would like to know more about our secure reporting process or submit a report yourself, please visit the reporting to CROSS-UK page.


A reporter is concerned that, if non approved sealants are used with CPVC sprinkler pipework and fittings, failures and/or leaks in those pipes can be caused due to environmental stress cracking or plasticization. This occurs when semi-volatile organic substances migrate from the sealant into the pipe or fitting. This can happen within a short time after installation or after several years. When leaks occur, this results in sprinkler circuits being turned off/drained down while failures are investigated, and repairs made. This can take several days or months, during which time there will be no protection from the sprinkler system.

In the opinion of the reporter, only sealants recommended by the specific sprinkler pipe manufacturers should be used. They report having seen failures in many premises because of this issue, where non approved sealants have been used. They suggest that the frequency of failures is increasing due to the increased use of residential sprinklers.

only sealants recommended by the specific sprinkler pipe manufacturers should be used

The reporter continues to describe other variables that affect the time to failure. These include environmental temperature (higher temperature favours failure) and lack of movement accommodation in the system. Hanger type and spacing also need to be in accordance with the pipe supplier's recommendations. The problem is further exacerbated when faced with overcrowded services at wall penetrations, e.g. through a 'letter box' type slot in the wall very close to the ceiling, with very little space to carry out removal and replacement of failed sections. This will inevitably lead to systems being shut off for longer to carry out remedial works.

Expert Panel Comments

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Expert Panels comment on the reports we receive. They use their experience to help you understand what can be learned from the reports. If you would like to know more, please visit the CROSS-UK Expert Panels page.

Use of correct sealants

It is important to make sure that installers only use a type of sealant that is specified as being acceptable for that particular type of pipe. Different types of pipe have different lists of approved sealants, so care should be taken.  

While this is a relatively simple issue, failure can have disastrous consequences such as failure of sprinklers during operation, flooding, and inoperative sprinklers leading to expensive and invasive remediation.


It is important to use contractors who can demonstrate their competence. Oversight of works should also pick up these relatively simple non-compliances.

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