How does friction loss influence the required discharge pressure when delivering a fixed nozzle flow?

• A. Higher friction loss requires higher discharge pressure.
• B. Higher friction loss reduces required discharge pressure.
• C. Friction loss has no effect on discharge pressure.
• D. Friction loss only affects pump RPM.

Answer: (A)

Friction losses in hoses and fittings create pressure drop between the pump discharge and the nozzle. When you’re delivering a fixed nozzle flow, the pump must supply enough pressure at the discharge to overcome those losses and still provide the nozzle with the required pressure for that flow. So, as friction loss increases, the pump must push more pressure to compensate.

Think of the total discharge pressure as the sum of the pressure needed at the nozzle plus the pressure lost to friction along the line (plus any elevation changes). If friction loss goes up, the required discharge pressure goes up as well.

This isn’t about RPM alone, and friction loss does affect discharge pressure. If friction loss increases, you don’t get away with a lower discharge pressure; you need more pressure to maintain the same nozzle flow.