Which statement describes a feature of 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 drain all sprinklers when opened.
• D. They alert the fire department when the sprinkler is dry.

Answer: (A)

Dry pipe valves control when water enters the sprinkler piping. In a dry pipe system, the pipes are charged with air (or nitrogen) and the water supply is held back by a dry pipe valve. When a sprinkler head is heated and releases, the pressure change allows the valve to admit water into the dry-pipe main, sending water through to the sprinklers. This setup keeps water out of the piping until a sprinkler is activated, which helps protect the system from freezing and provides a controlled, rapid delivery once a head is opened. The other statements don’t describe this mechanism: the system relies on air to keep water out until activation, it doesn’t drain all sprinklers when opened, and there’s no automatic fire department alert produced by the valve.