Which unit is used to express total flow rate in MWS calculations?

Which unit is used to express total flow rate in MWS calculations?

• A. gallons per hour (gph)
• B. pounds per square inch (psi)
• C. liters per second (L/s)
• D. gallons per minute (gpm)

Answer: (D)

Total flow rate tells you how much water moves through the system each minute. In MWS calculations, the standard unit is gallons per minute because pump and nozzle ratings are given in gpm, and you can easily add flows from multiple hoses to get a total. Pressure measures resistance, not quantity, so psi isn’t a flow unit. A metric option like liters per second could be used in other contexts, but the USAF MWS practice relies on gallons per minute. Gallons per hour is a valid volume-per-time unit, but it’s too coarse for firefighting calculations where you need the per-minute rate. So the total flow rate is expressed in gallons per minute.

Total flow rate tells you how much water moves through the system each minute. In MWS calculations, the standard unit is gallons per minute because pump and nozzle ratings are given in gpm, and you can easily add flows from multiple hoses to get a total. Pressure measures resistance, not quantity, so psi isn’t a flow unit. A metric option like liters per second could be used in other contexts, but the USAF MWS practice relies on gallons per minute. Gallons per hour is a valid volume-per-time unit, but it’s too coarse for firefighting calculations where you need the per-minute rate. So the total flow rate is expressed in gallons per minute.