Which statement correctly describes a dry-pipe sprinkler system?

• A. They keep pipes pressurized with air or nitrogen and fill with water upon activation.
• B. They keep pipes filled with water at all times.
• C. They require two-step verification before water enters the pipes.
• D. They deliver water to all heads simultaneously.

Answer: (A)

Dry-pipe systems keep the sprinkler piping charged with air or nitrogen, not water. The water is stored separately (in a reservoir or similar supply) and is released into the dry pipes when a sprinkler head is activated, causing the pipes to fill with water. This setup helps prevent freezing in unheated spaces and provides a controlled, slower response compared to systems where water is in the pipes all the time. The other statements describe wet-pipe systems, or features that aren’t part of how a dry-pipe system operates, such as a requirement for a verification step or all heads delivering water at once.