Which term describes the pressure in a system after subtracting the hydrant inlet pressure from the pump discharge?

• A. Net Pump Discharge
• B. Maximum Discharge
• C. Residual
• D. Pump Intake

Answer: (A)

Net pump discharge pressure is the pressure actually available in the hose system after you subtract the hydrant inlet pressure from the pump’s discharge pressure. This value shows how much pressure you have to overcome friction losses and reach the nozzle, once the source’s supply pressure is accounted for. For example, if the pump discharge reads 150 psi and the hydrant inlet is delivering 60 psi, the net pump discharge pressure is 90 psi. That net figure is what you use to calculate hose friction losses and to set the correct nozzle pressure. The other terms don’t fit this idea: residual describes remaining pressure in the system after something else is added, maximum discharge refers to the pump’s capacity, and pump intake concerns the suction side.