What is friction loss and how does it affect pump operation?

• A. Friction loss is the pressure loss due to flow through piping and fittings; higher flow increases friction loss and raises required discharge pressure.
• B. Friction loss is the pressure increase across pipes.
• C. Friction loss is the water temperature drop in the system.
• D. Friction loss is the energy gained by water as it moves.

Answer: (A)

Friction loss is the pressure drop that happens as water flows through pipes, fittings, valves, and other components. The resistance from pipe walls and fittings increases with flow velocity, length of piping, and roughness, so pushing more water through the system causes more pressure to be lost along the line. Because this loss uses up part of the pump’s head, higher discharge flow requires higher discharge pressure to achieve the same downstream pressure. In firefighting pump practice, you must account for friction loss when selecting the pump and setting discharge pressures, ensuring the pump can deliver the required pressure at the desired flow despite the losses in the piping network. Friction loss is a pressure drop, not a pressure increase; it’s not a temperature change or energy gain for the water.