What does a waterflow switch do in a sprinkler system?

• A. It detects water movement in the sprinkler pipes and triggers a fire alarm event when water flow is detected.
• B. It detects humidity in the building.
• C. It controls the sprinkler valve to release water on command.
• D. It records water usage for billing.

Answer: (A)

The waterflow switch is there to sense movement of water inside the sprinkler pipes. It uses a small mechanism—like a paddle or turbine—that is moved when water starts flowing, such as when a sprinkler head is released or a line is active. When it detects flow, it sends a signal to the fire alarm system to indicate that water is moving, which triggers the alarm. This lets responders know that the system has discharged water, which is critical for a timely alert.

Humidity sensors and devices that control valves serve different purposes. Humidity sensing looks at ambient air moisture, not water in the pipes. The sprinkler valve is usually operated by the fire protection system itself, not forced by the flow switch. Metering water usage for billing is a separate function not tied to alarm signaling.