TL;DR
A waterflow switch is the detection device on a fire sprinkler riser or branch line whose paddle, inserted in the pipe, deflects when water starts moving and signals the alarm panel that a sprinkler head has opened. A built-in retard mechanism delays the signal up to about 90 seconds so municipal pressure surges do not trigger false alarms.
What it means
A waterflow switch is the detection device on a fire sprinkler riser or branch line whose paddle, inserted in the pipe, deflects when water starts moving and signals the alarm panel that a sprinkler head has opened. A built-in retard mechanism delays the signal up to about 90 seconds so municipal pressure surges do not trigger false alarms. NFPA 72 requires testing them, typically semiannually, by opening the inspector's test connection that simulates the flow of one head, and the alarm must sound within the retard window for the system to pass.
Where it sits in the glossary
Waterflow switch is part of the Trade jargon group inside the ProFix Directory glossary. Browse every term in this category from the glossary index.
Why Ohio homeowners should know it
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See also
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