In which type of sprinkler system is the piping filled with pressurized air instead of water?

In which type of sprinkler system is the piping filled with pressurized air instead of water?

• A. Deluge
• B. Wet-pipe
• C. Dry pipe
• D. Delayed-pipe

Answer: (C)

Dry pipe systems are designed so the piping is charged with pressurized air (or nitrogen) rather than water. A dry-pipe valve holds back water in a separate supply; when a sprinkler head is activated, the air pressure drops, the valve opens, and water is released into the piping to reach the activated head. This setup prevents freezing in unheated spaces and reduces the risk of water damage from leaks before a fire is detected. The trade-off is a slight delay between activation and water reaching the heads, due to the need to purge air and fill the pipes.

Dry pipe systems are designed so the piping is charged with pressurized air (or nitrogen) rather than water. A dry-pipe valve holds back water in a separate supply; when a sprinkler head is activated, the air pressure drops, the valve opens, and water is released into the piping to reach the activated head. This setup prevents freezing in unheated spaces and reduces the risk of water damage from leaks before a fire is detected. The trade-off is a slight delay between activation and water reaching the heads, due to the need to purge air and fill the pipes.