A system that activates only when the detection system activates, but does not activate when a sprinkler opens is a __________ pre action system.

A system that activates only when the detection system activates, but does not activate when a sprinkler opens is a __________ pre action system.

• A. Double interlock
• B. Deluge
• C. Wet pipe
• D. Single interlock

Answer: (D)

Pre-action sprinkler systems are designed to prevent accidental discharge by requiring a trigger before water is released into the piping. In a single interlock pre-action, the water-filled piping remains dry until a detection device is activated. The system’s water is admitted only after that detection event, so simply opening a sprinkler head won’t release water by itself. This means the system responds to the detection signal, not just to a sprinkler head actuation, which matches the described scenario. In contrast, other pre-action types or wet/deluge systems operate differently and would not fit this behavior as cleanly.

Pre-action sprinkler systems are designed to prevent accidental discharge by requiring a trigger before water is released into the piping. In a single interlock pre-action, the water-filled piping remains dry until a detection device is activated. The system’s water is admitted only after that detection event, so simply opening a sprinkler head won’t release water by itself. This means the system responds to the detection signal, not just to a sprinkler head actuation, which matches the described scenario. In contrast, other pre-action types or wet/deluge systems operate differently and would not fit this behavior as cleanly.