What is pump discharge pressure?

• A. The pressure the pump must develop to deliver water to the nozzle, accounting for NP and friction losses
• B. The pressure at the nozzle used to produce the fire stream
• C. Pressure loss due to friction in hose and fittings
• D. Atmospheric pressure

Answer: (A)

Pump discharge pressure is the pressure the pump must develop at its discharge to push water through the hose to the nozzle, meeting the nozzle’s required pressure. To determine it, you add the nozzle pressure (the pressure the nozzle needs to produce the fire stream) to all friction losses along the hose and fittings, plus any elevation losses along the line. For example, if the nozzle requires 100 psi and the hose/friction losses add up to 40 psi, the pump discharge pressure needs to be about 140 psi (ignoring elevation). Atmospheric pressure isn’t a factor in this firefighting context, and friction losses alone don’t capture the total pressure the pump must supply—those losses must be added to the nozzle pressure.