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

The component that allows water into an automatic dry-pipe sprinkler system is the dry-pipe valve. This valve is designed to hold back water from the system pipes until a fire is detected. It is filled with pressurized air or nitrogen which keeps the water from entering the pipes. When a fire occurs and one of the sprinkler heads activates, the air pressure in the system drops, causing the dry-pipe valve to open. This allows water to flow into the sprinkler pipes and out through the activated sprinkler head, thus effectively combating the fire.

The role of the dry-pipe valve is crucial in preventing water damage in areas where freezing may occur, as the system remains dry until needed. Other components like the pressure tank, flow switch, and air compressor serve different functions in the system, such as maintaining system pressure, detecting water flow, and maintaining air pressure respectively, but they do not directly allow water into the system in the manner that the dry-pipe valve does.