What is the difference between the pump discharge pressure and the incoming pressure from the hydrant called?

The difference between the pump discharge pressure and the incoming pressure from the hydrant is known as net pump discharge. This term refers specifically to the effective pressure generated by the pump after accounting for any pressure loss due to friction or elevation changes in the hose or water system.

When a fire apparatus is pumping water, the incoming pressure from the hydrant and the discharge pressure at the end of the hose can be significantly different due to various factors such as hose length, diameter, and terrain. Net pump discharge provides a clear understanding of the actual pressure that the pump is producing to deliver water effectively to the fire scene, making it a vital measurement for firefighters to ensure they have adequate pressure to combat fires.

Static pressure refers to the pressure in the system when there is no flow, while residual pressure is the pressure remaining in the system when water is being withdrawn. Total pressure is the sum of all pressures in a system but does not specifically address the difference between incoming and discharge pressures. These terms serve different functions in understanding fire hydrant systems, but it is net pump discharge that specifically describes the difference sought in the question.