Which method can be used to verify hydrant flow?

• A. Waving a handkerchief in the breeze.
• B. Using a flow meter or applying friction loss calculations.
• C. Measuring the water's pH.
• D. Estimating by feel.

Answer: (B)

Verifying hydrant flow relies on obtaining a reliable measurement of discharge from the hydrant. The best way to do this is to use a flow meter to directly measure the actual flow rate, or to compute it from friction losses in the hose line and other known pressures. A flow meter gives a straightforward gallons-per-minute reading, which is the most accurate way to confirm how much water the hydrant can deliver. If a flow meter isn’t available, you can estimate flow by applying friction loss calculations, using the hose diameter and length, the measured pressure losses, and standard friction loss data. This approach ties the observed pressure drop to a calculated flow rate, aligning with established testing practices.

Waving a handkerchief in the breeze, measuring pH, or guessing by feel don’t provide a meaningful or reliable measure of how much water a hydrant can deliver, so they aren’t appropriate methods for verifying hydrant flow.