What does friction loss represent in pump operations?

• A. Pressure drop from water moving through hose and fittings
• B. Pressure gained from elevation
• C. Pressure at nozzle
• D. Pressure due to engine RPM

Answer: (A)

Friction loss is the pressure drop caused by water rubbing against the interior walls of hose and through fittings as it flows. The flow faces resistance from the hose length, diameter, roughness, and the number of fittings and valves in the path, so more length, smaller hose, or more fittings raise the loss. This pressure drop reduces the amount of pressure available at the nozzle, even though the pump may be delivering a higher discharge pressure. Elevation changes create static head, but friction loss specifically measures the dynamic resistance along the hose and fittings. Engine RPM affects overall pump output, but friction loss is about the resistance in the hose system itself.