A pre-action system that activates only when the detection system is triggered is called a ______ pre-action system.

A pre-action system that activates only when the detection system is triggered is called a ______ pre-action system.

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

Answer: (A)

A pre-action system uses a trigger to release water into piping, preventing leaks or accidental discharge. The number of triggers defines the interlock type. When the system activates only after the detection system is triggered, it’s using a single interlock. Here, the detection actuation is the sole event needed to prepare the system for water flow, making the pipes ready to deliver water when a sprinkler head is activated. This differs from a double interlock, which requires two separate events (for example, detection plus a second release action) before water can enter the piping. Deluge systems provide water to all sprinkler heads once the system is opened, and wet pipe systems have water-filled pipes that release immediately when any head is activated.

A pre-action system uses a trigger to release water into piping, preventing leaks or accidental discharge. The number of triggers defines the interlock type. When the system activates only after the detection system is triggered, it’s using a single interlock. Here, the detection actuation is the sole event needed to prepare the system for water flow, making the pipes ready to deliver water when a sprinkler head is activated.

This differs from a double interlock, which requires two separate events (for example, detection plus a second release action) before water can enter the piping. Deluge systems provide water to all sprinkler heads once the system is opened, and wet pipe systems have water-filled pipes that release immediately when any head is activated.