Manufacturers are working to improve CPVC installation education.

NFPA Journal®, May/June 2008

The use of nonmetallic pipe in fire sprinkler systems is fairly modern, but there have been several distinct eras involving different types of products. As manufacturers of some types of nonmetallic piping seek broader acceptance, others are working to ensure the use of best practices for installation and use.

The first nonmetallic material listed for use in fire sprinkler system pipes was polybutylene, a flexible piping product joined by a heat fusion technique that came onto the scene in 1983. It showed great promise, but within a decade, failures in plumbing systems led to a class action lawsuit and the end of polybutylene fire sprinkler piping.

The most recent nonmetallic sprinkler piping product, cross-linked polyethylene (PEX), was first accepted in 1999, but only for use in combined sprinkler and plumbing systems for dwellings to which NFPA 13D, Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes, applied. Because the PEX doesn’t have the same pressure capability at elevated temperatures as previously listed nonmetallic sprinkler piping, the Technical Committee on Residential Sprinkler Systems decided that a reduced pressure rating would be allowed if limitations and the use of the domestic water system precluded exposure to high sprinkler system pressures. As the 2010 edition of NFPA 13D is being prepared, one of the issues facing the technical committee is whether the connection of a single domestic fixture to the sprinkler system, a concept the committee has named a “passive purge” system affords the same protection.

Chlorinated polyvinyl chloride (CPVC) sprinkler pipe followed the original polybutylene listing by about two years, and has been successful since it was introduced. Manufacturers report that more than a billion feet of CPVC sprinkler piping have been installed in applications complying with NFPA 13D and NFPA 13R, Installation of Sprinkler Systems in Residential Occupancies up to and Including Four Stories in Height applications and in light hazard NFPA 13, Installation of Sprinkler Systems, applications. Even with a product this established, CPVC pipe and fittings manufacturers seek to prevent problems by cooperating to standardize installation instructions, warning labels, and other aspects of use.

The biggest concern is product compatibility. Lubrizol Corp., formerly Noveon®, Inc., has had a chemical compatibility approval program in place for its BlazeMaster® CPVC piping for several years. The program mainly addresses ancillary items such as thread sealants and antifreeze solutions, but it also includes insulation materials, seismic separation assemblies, and flexible drops, more than 50 products in all. BlazeMaster’s website, www.blazemaster.com, also lists nearly 50 unacceptable products.

The main concern is the potential for environmental stress cracking over time. These compatibility issues must be recognized by general contractors, other trades at the work site, authorities having jurisdiction, property owners and maintenance people, and fire sprinkler contractors.

All nonmetallic piping products have come into the NFPA sprinkler standards as special listed products. Successful special listed products such as CPVC have gradually been addressed more generically over the years. Although most new compatibility issues relate to the use and handling of materials at the job site, engineers and technicians should follow best practices when specifying CPVC and other nonmetallic piping products and when acknowledging the use of such products in combination with building interfaces.