Section 8.3.1/Types of Sprinkler Systems
NFPA 13 Section 8.3 defines wet pipe, dry pipe, preaction, and deluge sprinkler system types and when each is required.
Sprinkler systems are classified into four types. Wet pipe systems maintain water in the piping at all times and are the most common and reliable type. Dry pipe systems use pressurized air or nitrogen in the piping, with water held at a dry pipe valve until a sprinkler operates; these are required in spaces subject to freezing. Preaction systems require both a detection event and a sprinkler operation before water flows, used in areas where accidental water discharge would cause significant damage (data centers, museums). Deluge systems have open sprinklers that all discharge simultaneously when the system activates, used for high-hazard areas (aircraft hangars, chemical storage).
Why this section exists
Different environments require different sprinkler system responses. A wet pipe system in an unheated parking garage would freeze and burst. A standard wet pipe system in a data center risks accidental water discharge from a mechanical impact. A standard system in an aircraft hangar cannot suppress a fast-developing fuel fire because it waits for individual sprinklers to open sequentially. Matching the system type to the hazard ensures effective fire suppression while minimizing unintended water damage.
What plan reviewers look for
Plan reviewers check the sprinkler riser diagram and system description for the system type. They verify that wet pipe systems are not used in freezing areas. They check that preaction systems include the required detection system and supervisory features. For dry pipe systems, they verify the maximum allowable pipe volume and the water delivery time to the most remote sprinkler (60 seconds maximum for most systems).
Common violations
Related NFPA 13 requirements
Section 8.5.1 covers sprinkler spacing for all system types. Section 7.2 covers dry pipe system specific requirements. Section 7.3 covers preaction system requirements. Section 7.4 covers deluge system requirements. Section 6.1.1 covers water supply requirements for all system types.