A type of sprinkler system that maintains air under pressure in the sprinkler piping is:

• A. dry pipe
• B. wet pipe
• C. deluge
• D. wet chemical

Answer: (A)

Dry pipe systems keep the sprinkler piping filled with pressurized air (or nitrogen) rather than water. A dry-pipe valve holds water back at the supply, and when a sprinkler head is activated, the valve opens and water flows into the piping, displacing the air and delivering water to the activated head. This arrangement protects piping in unheated or remote areas from freezing and reduces the chance of accidental water damage while the system sits idle. In contrast, wet pipe systems have water-filled piping that delivers water immediately when a head is opened, deluge systems have all sprinkler piping filled with water with all heads open, and wet chemical systems are designed for commercial kitchens and use a chemical agent rather than water.