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Q&A: Installation of Plastic Fire Sprinkler Pipe in Exposed Locations

All of your area plastic fire sprinkler pipe questions answered.

December 2, 2019

Q: Is non-metallic piping allowed to be used for fire sprinkler piping? If so, what installation codes address these products?

A: The answer can be found in Section 7.3.2 of NFPA 13-2019, Standard for the Installation of Sprinkler Systems, which includes requirements for nonmetallic fire sprinkler pipe and tubing to be investigated for suitability in automatic sprinkler installation. This section requires non-metallic piping to comply with testing standards (found in Table based on the specific type of non-metallic material of which the piping is fabricated and for the piping to be listed for use in an automatic sprinkler system.

NFPA 13 allows the use of other types of nonmetallic pipe or tube (differing from those identified in Table to be investigated for suitability in automatic sprinkler installations and listed for this service. This includes CPVC, or other materials, when installed in accordance with their listing limitations.

Table refers to ASTM F442/F442M, Standards Specification for Chlorinate Poly(vinyl Chloride) (CPVC) Plastic Pipe (SDR-PR) for material and dimensional requirements for CPVC. Section also allows for other materials to be used.

As noted in both sections of 7.3.2, nonmetallic pipe is required to be listed for fire protection service. UL has a certification program for non-metallic pipe that utilizes UL 1821, the Standard for Safety of Thermoplastic Sprinkler Pipe and Fittings for Fire Protection Service.

UL 1821 covers thermoplastic pipe for use in light hazard occupancies as defined in NFPA 13 and residential occupancies as defined in both NFPA 13R-2019, Standard for the installation of Sprinkler Systems in Low-Rise Residential Occupancies and NFPA 13D-2019, Standard for the Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes. Both NFPA 13R and NFPA 13D require nonmetallic pipe to be listed.


Q: What type of protection is required for use of non-metallic piping and can it ever be installed without protection?

A: Nonmetallic piping is required to be installed in accordance with its certification  requirements including protecting the pipe by any one of the following methods:

  • 3/8 inch (9.5 mm) thick or thicker gypsum wallboard
  • A suspended membrane ceiling with lay-in panels or tiles having a weight of not less than 0.35 lb./ft (1.76 kg/m2) when installed with metallic support grids
  • 1/2 inch (12.7 mm) plywood soffits

If pipe is intended to be installed in exposed applications, UL evaluates the non-metallic pipe and fittings in accordance with UL 1821 which requires fire testing specific for this type of installation intended to be used in exposed applications.  If the product meets the requirements of the Standard for exposed applications, the manufacturers installation instructions will indicate the limitations of use in such applications.


Q: What types of non-metallic pipe has UL certified? Are any of them certified for use in exposed basement applications?

A: For this application, UL certifies chlorinated poly vinyl chloride (CPVC) and crosslinked polyethylene (PEX) non-metallic pipe and fittings. 

Some manufacturers have UL certified CPVC for use in exposed basement applications and these pipes and fittings may be installed without the prescriptive protection noted above, but must precisely follow the manufacturer’s installation instructions and comply with any limitations regarding installation location or method.

As of now, UL has not certified any PEX piping for exposed basement applications. 

UL certification requirements and certified CPVC sprinkler pipe and fittings can be found in the UL product category (VIWT). Additional guide Information about this category can be found by using our UL Product iQTM. Product iQ is free with a one-time registration.


Visit for information on fire sprinkler testing and certification services.