Which sprinkler system uses water-filled pipes that release water immediately when a sprinkler head is activated?

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

Answer: (B)

Wet-pipe systems keep water in the piping at all times, so when a sprinkler head is heated enough to activate, the valve opens and water flows immediately through that head. This provides the quickest response because there’s no delay waiting for water to fill the pipes.

In contrast, dry-pipe systems have piping filled with pressurized air or nitrogen and water must be released into the pipes from a main valve before it reaches the heads, causing a delay. Deluge systems have pipes that are typically filled with water, but all heads are open and water is released through every head when the system activates. Pre-action systems require a detection or interlock step before water enters the pipes, adding another delay.