Which sprinkler system requires an additional triggering event before water is released into the pipes?

• A. Wet-pipe
• B. Dry-pipe
• C. Pre-action
• D. Deluge

Answer: (C)

Requiring a separate triggering action before water enters the pipes is what defines a pre-action sprinkler system. In this setup, the piping isn’t normally filled with water; a detection event or other specified trigger must occur first. Once that event happens—such as a heat/smoke detector being activated or a manual release—the valve permits water to enter the pipes and the sprinklers discharge. This two-step process is designed to prevent accidental releases in areas where false alarms or unintended activations could occur.

In contrast, wet-pipe systems have water-filled pipes that release water immediately when a sprinkler head is activated by heat. Dry-pipe systems keep the pipes charged with air or nitrogen and release water into the dry pipes when a sprinkler head is activated, though there may be a delay as water moves into the piping. Deluge systems have all sprinkler heads open and release water to all heads as soon as the system is activated, with no preliminary triggering step.