What is the maximum delay allowed for a waterflow switch in a typical fire alarm system?

• A. 60 sec
• B. 90 sec
• C. 120 sec
• D. 180 sec

Answer: (B)

Waterflow switches are initiating devices that trigger the fire alarm when water begins to move through the sprinkler piping. The delay before the alarm signals the control panel is there to balance quick notification with avoiding nuisance alarms from non-fire flows or transient events. In typical fire alarm designs, this delay is limited to about 90 seconds, providing a prompt alert—roughly a minute and a half after water flow starts—while still allowing a short settling period to prevent false alarms. Delays much shorter could lead to more false activations, and longer delays would risk delaying life-safety notification, so 90 seconds is the common, practical maximum.