If the target nozzle pressure is 100 psi, and total friction losses are 25 psi with 15 psi elevation losses, what is the required initial discharge pressure?

• A. 125 psi
• B. 150 psi
• C. 140 psi
• D. 110 psi

Answer: (C)

To deliver the target nozzle pressure, you must account for all losses along the hose line. The pump discharge pressure needs to cover both the friction losses in the hose and any elevation losses, while still leaving the nozzle at the desired pressure.

Add the losses to the nozzle pressure: 100 psi (nozzle) + 25 psi (friction) + 15 psi (elevation) = 140 psi. So the required initial discharge pressure from the pump is 140 psi.

If a number like 125 psi were chosen, it wouldn’t overcome the elevation loss; 150 psi would oversupply beyond what’s needed; and 110 psi would not overcome the losses enough to maintain the nozzle at 100 psi.