What is a water-flow switch and what does it signal to the fire alarm panel?

• A. A device that detects water pressure in the sprinkler piping.
• B. A device that detects air movement in the sprinkler headers.
• C. A device that detects sprinkler head temperature.
• D. A device that detects water movement in the sprinkler system and transmits an alarm signal to the panel when a sprinkler head discharges water.

Answer: (D)

A water-flow switch is a device that detects movement of water in the sprinkler piping when a sprinkler head discharges. When water starts to flow, the switch is actuated and sends an alarm signal to the fire alarm panel, triggering the alarm and system response.

This isn’t about measuring pressure, air movement, or temperature. A pressure switch watches for changes in water pressure, an air-movement detector would monitor air flow (not typical for sprinkler flow), and a temperature device responds to heat on a sprinkler head. The key idea is that the water moving through the system after a head releases water is what the switch detects and reports to the panel.