During hydrant nozzle testing, what is the minimum duration for which the flow nozzle should run?

During hydrant nozzle testing, what is the minimum duration for which the flow nozzle should run?

• A. 30 seconds
• B. 1 minute
• C. 2 minutes
• D. 5 minutes

Answer: (B)

You need a steady, representative discharge to calculate the flow rate accurately. When the hydrant nozzle is opened, air must be purged, the water column stabilizes, and system pressures settle. If the flow is measured too soon, you capture a transient surge or fluctuating readings rather than a true, steady flow, which can skew the discharge calculation. Allowing the flow nozzle to run for about a minute gives enough time for the flow and pressures to stabilize, producing a reliable, repeatable reading. Longer runtimes don’t significantly improve accuracy and simply slow the test.

You need a steady, representative discharge to calculate the flow rate accurately. When the hydrant nozzle is opened, air must be purged, the water column stabilizes, and system pressures settle. If the flow is measured too soon, you capture a transient surge or fluctuating readings rather than a true, steady flow, which can skew the discharge calculation. Allowing the flow nozzle to run for about a minute gives enough time for the flow and pressures to stabilize, producing a reliable, repeatable reading. Longer runtimes don’t significantly improve accuracy and simply slow the test.