1 Scope

1.1 These requirements cover primary carrier, secondary containment, integral primary/secondary containment, normal vent and vapor recovery, nonmetallic pipe, fittings, and systems (products) intended for use underground in the distribution of petroleum-base flammable and combustible liquids, alcohols, and alcohol-blended fuels as identified in this Standard.

1.2 The piping covered by these requirements is intended to be installed and used in accordance with the Flammable and Combustible Liquids Code, NFPA 30 and the Standard for Automotive and Marine Service Station Code, NFPA 30A.

1.3 These requirements cover nonmetallic thermoplastic (flexible) and thermoset (rigid) plastic piping with manufacturer-supplied fittings for underground use only. The products covered by this Standard have been evaluated for assembly in normal soil applications by qualified persons in accordance with the manufacturer’s instructions.

1.4 The products covered by this Standard have not been evaluated for applications in sumps [more than 12 inches (30.5 cm) from sump wall], as connector pipe (between underground pipe and dispensing device), aboveground or marine use, or other applications exceeding ambient temperatures of 75 °F (23 °C).

Summary of Topics

This new Third Edition of UL 971 dated December 3, 2025 includes the following changes in requirements:

– Correction of Interstitial Communication Requirement; 19.2.

– Correction to 8.2.3.

– Updates to Table 6.1.

– Editorial updates 17.3.1, 17.4.1, and 20.3.

– Miscellaneous updates to align the document with the current Style Manual.