What is the term for the part of the total pressure not used to overcome friction or gravity while forcing water through hose and fittings?

Residual pressure refers to the portion of the total pressure available in a fire hose system that remains after accounting for the losses due to friction and elevation when water is pushed through hoses and fittings. This concept is crucial to understanding how much pressure is still available to effectively deliver water to the nozzle and achieve desired flow rates at the discharge point.

In a firefighting context, pressure drops occur in the system due to resistance in the hose and fittings (friction) and due to the vertical distances water must be lifted (gravity). The residual pressure indicates how much pressure is left to contribute to the actual flow of water once these losses have been deducted from the total pressure generated by the pump.

Understanding residual pressure helps firefighters assess the effectiveness of the pumping system and ensures they can achieve adequate flow rates to combat fires effectively. By monitoring this pressure, operators can manage the system to maintain efficient operations and make adjustments as needed depending on the conditions encountered in the field.