What is the desired pump pressure when supplying two lines of 2-1/2 inch hose, one 200 feet long and one 300 feet long, each with a 250 gpm nozzle operating at 100 psi?

• A. 107.5 psi
• B. 162.5 psi
• C. 137.5 psi
• D. 125.5 psi

Answer: (C)

When feeding two lines, the pump must overcome the nozzle pressure plus the friction losses along each hose and then sum those losses. Each line carries 250 gpm, so the friction loss per line is the same. For 2-1/2 inch hose at 250 gpm, the friction loss is about 7.5 psi per 100 feet.

Compute the losses by length: for 200 feet, the loss is (200/100) × 7.5 = 15 psi. For 300 feet, the loss is (300/100) × 7.5 = 22.5 psi. The total friction loss is 15 + 22.5 = 37.5 psi.

Add the nozzle pressure (the pressure required at the nozzle) to get the pump discharge pressure: 100 + 37.5 = 137.5 psi.

So, the needed pump pressure is 137.5 psi.