Which components are included in discharge pressure calculations alongside nozzle pressure?

• A. Discharge pressure includes nozzle pressure, total friction losses in attack and supply lines, and any elevation losses.
• B. Discharge pressure includes only nozzle pressure.
• C. Discharge pressure includes nozzle pressure and air temperature.
• D. Discharge pressure includes pump RPM and engine torque.

Answer: (A)

Discharge pressure is the pressure you must deliver at the pump discharge to achieve the nozzle pressure you need. To determine it, start with the nozzle pressure and then add the hydraulic losses the water encounters on its path: the total friction losses in both the attack line and the supply line, plus any elevation losses from changes in height. Elevation losses occur when pumping uphill, increasing the requirement, while downhill elevation would reduce the needed discharge pressure. Air temperature does not factor into this calculation, and pump RPM or engine torque don’t directly set discharge pressure—they influence overall pump performance but aren’t added as part of the discharge pressure sum. So the correct approach is nozzle pressure plus friction losses in both lines plus elevation losses.