1 Scope

1.1 These requirements cover thermoplastic pipe and fittings for use in wet pipe sprinkler systems for fire protection service.

1.2 Thermoplastic pipe and fittings covered by these requirements are intended for use in sprinkler systems in any of the following types of occupancies:

1. a) Light hazard occupancies as defined in the Standard for Installation of Sprinkler Systems, NFPA 13;

2. b) Residential occupancies as defined in the Standard for Installation of Sprinkler Systems in One- and Two-Family Dwellings and Manufactured Homes, NFPA 13D; and

3. c) Residential occupancies as defined in the Standard for Installation of Sprinkler Systems in Low-Rise Residential Occupancies, NFPA 13R.

Summary of Topics

This revision of ANSI/CAN/UL 1821 dated November 10, 2025 includes revised requirements from proposals dated June 6, 2025 and September 26, 2025: 9.7, 9.8, 12.1, 19.1, 20.2A, 21.2A, 23.4, 24.2A, 24.4, Figure 24.1, 25.2A, 26.2A, 31.7, Figure 31.1, Figure 31.2, 31.8, 31.9, Table 27.1, and Table 28.1.