Which statement is true about dry pipe valves?

• A. They keep water out of the sprinkler system until a fire activates a sprinkler.
• B. They allow air to enter the sprinkler system.
• C. They alert the fire department when the sprinkler system is dry.
• D. They drain all sprinklers when they are opened.

Answer: (A)

In a dry pipe system, the piping is kept full of air or gas, not water, and a dry pipe valve holds back the water supply. When a sprinkler head is activated, the valve opens and water rapidly flows into the piping to reach the sprinklers, pushing air out as the system fills with water. This means water is kept out of the sprinkler piping until a fire triggers a head, which is what the true statement describes.

The other ideas don’t fit because the dry pipe valve isn’t designed to let air into the system (the system already contains air and the valve’s role is to release water), it doesn’t alert the fire department by itself, and opening it doesn’t drain all sprinklers—the water fills the system rather than draining it.