What is the primary purpose of using a pitot gauge in hydrant flow testing?

• A. To determine hydrant discharge flow
• B. To measure air pressure in the system
• C. To gauge water temperature
• D. To calibrate the pressure relief valve

Answer: (A)

Measuring how fast water moves in the hydrant stream is essential to determine discharge flow. A pitot gauge captures velocity pressure, the dynamic pressure related to the water’s speed. By inserting the pitot tube into the flowing water, the gauge reads velocity pressure. Using the hydrant outlet size and this velocity pressure, you convert the reading into a discharge flow (gallons per minute) with a standard flow equation or calibration table. This is why the pitot gauge is used in hydrant flow testing—to determine the hydrant’s discharge flow. It isn’t used to measure static air pressure, water temperature, or to calibrate a pressure relief valve.