What allows water into an automatic dry-pipe sprinkler system?

The automatic dry-pipe sprinkler system operates by utilizing a dry-pipe valve, which is crucial for allowing water into the system when activated. This valve is designed to hold back water in the supply line, keeping the pipe system filled with air or nitrogen until the system is triggered by heat from a fire. When a sprinkler head opens due to the elevated temperature, the change in pressure allows the dry-pipe valve to open, permitting water to flow into the system and ultimately extinguishing the fire.

In contrast, the other components mentioned have different roles within the fire protection system. For instance, the control valve is essential for managing the overall flow and direction of water in the system but does not specifically facilitate the entry of water into a dry-pipe sprinkler system. The pressure regulator maintains the appropriate pressure levels in the system, ensuring that sprinklers operate effectively but does not control the entry of water. The alarm valve is primarily designed to signal the activation of the fire protection system, providing alerts when water flow occurs, but it does not function to allow water into the system.