Given a 60 psi nozzle pressure and 12 psi friction loss over 150 feet of 2.5-inch hose delivering 150 GPM, what is the discharge pressure?

Given a 60 psi nozzle pressure and 12 psi friction loss over 150 feet of 2.5-inch hose delivering 150 GPM, what is the discharge pressure?

• A. 60 psi
• B. 72 psi
• C. 54 psi
• D. 120 psi

Answer: (B)

The needed concept is that pump discharge pressure must overcome friction losses in the hose while still delivering the desired nozzle pressure. So you add the friction loss to the nozzle pressure to get the discharge pressure. Here, nozzle pressure is 60 psi and friction loss over 150 ft of 2.5-inch hose at 150 GPM is 12 psi. Add them: 60 + 12 = 72 psi. That’s why the correct discharge pressure is 72 psi. The other numbers would come from ignoring friction (60 psi), subtracting the loss (54 psi), or misapplying the loss (120 psi), which doesn’t reflect the required combination of nozzle pressure plus friction loss.

The needed concept is that pump discharge pressure must overcome friction losses in the hose while still delivering the desired nozzle pressure. So you add the friction loss to the nozzle pressure to get the discharge pressure.

Here, nozzle pressure is 60 psi and friction loss over 150 ft of 2.5-inch hose at 150 GPM is 12 psi. Add them: 60 + 12 = 72 psi. That’s why the correct discharge pressure is 72 psi.

The other numbers would come from ignoring friction (60 psi), subtracting the loss (54 psi), or misapplying the loss (120 psi), which doesn’t reflect the required combination of nozzle pressure plus friction loss.