What is the difference between wet-pipe and dry-pipe systems?

What is the difference between wet-pipe and dry-pipe systems?

• A. Wet-pipe systems hold pressurized air or nitrogen
• B. Dry-pipe systems have water-filled piping
• C. Wet-pipe piping is water-filled; dry-pipe holds pressurized air or nitrogen in the pipes; water enters when a head is activated in a dry-pipe
• D. Dry-pipe systems are not used for fire protection

Answer: (C)

The main idea is what fills the pipes and how water reaches the sprinklers. In a wet-pipe system, the piping is always filled with water, so when a sprinkler head is heated and releases, water immediately flows through the lines to the activated head. In a dry-pipe system, the pipes are kept under pressure with air or nitrogen, and water is held back in a separate vessel. Water only enters the piping after a dry-pipe valve is released by a sprinkler head, so there’s a brief delay as the pipes fill and water moves to the head. This setup makes wet-pipe simpler and faster to discharge, while dry-pipe is better for unheated or cold spaces where water-filled pipes could freeze, at the cost of more complexity and a little delay in water delivery. The statement that dry-pipe systems are not used for fire protection is incorrect, since both types are designed for fire suppression.

The main idea is what fills the pipes and how water reaches the sprinklers. In a wet-pipe system, the piping is always filled with water, so when a sprinkler head is heated and releases, water immediately flows through the lines to the activated head. In a dry-pipe system, the pipes are kept under pressure with air or nitrogen, and water is held back in a separate vessel. Water only enters the piping after a dry-pipe valve is released by a sprinkler head, so there’s a brief delay as the pipes fill and water moves to the head.

This setup makes wet-pipe simpler and faster to discharge, while dry-pipe is better for unheated or cold spaces where water-filled pipes could freeze, at the cost of more complexity and a little delay in water delivery. The statement that dry-pipe systems are not used for fire protection is incorrect, since both types are designed for fire suppression.