If friction loss increases on a run while maintaining the same nozzle flow, what adjustment is typically required to maintain nozzle pressure?

If friction loss increases on a run while maintaining the same nozzle flow, what adjustment is typically required to maintain nozzle pressure?

• A. Increase discharge pressure
• B. Decrease discharge pressure
• C. Increase hose diameter
• D. Shorten the run

Answer: (A)

When you’re delivering water at a set nozzle flow, the pressure at the nozzle is the pump discharge pressure minus all friction losses along the hose and fittings. If friction loss increases on the run, the nozzle won’t see enough pressure unless you raise the pump discharge pressure to offset that extra loss. In practice, you would increase the discharge pressure by the amount the friction loss has increased so the nozzle pressure remains what the nozzle requires for that flow.

For example, if the nozzle requires 100 psi and the friction loss was 25 psi, the pump discharge pressure would be about 125 psi. If friction loss climbs to 35 psi, you’d raise discharge pressure to about 135 psi to keep the nozzle at 100 psi.

Lowering discharge pressure would reduce nozzle pressure, and changing hose diameter or shortening the run isn’t typically an on-the-fly adjustment during a live run to compensate for increased friction.