Acronyms & Units
GPM
Gallons Per Minute
GPM stands for gallons per minute, the unit of flow used throughout pump operations. It measures how much water a line is moving, which drives friction loss, tank duration, and fire-knockdown power.
Flow is the quantity most pump-operations numbers hinge on, and gpm is how it is expressed. A nozzle's rating, a hydrant's capacity, and a tank's drain rate are all stated in gallons per minute.
Because friction loss grows with the square of the flow, even modest changes in gpm move the pump pressure noticeably. Thinking in gpm keeps the operator connected to the cause behind the gauge readings.
Where this shows up
Calculator
Tank Duration