What is friction loss and why is it important to calculate?

• A. Pressure gain caused by elevation changes; not required to calculate.
• B. Pressure loss due to piping, fittings, and hoses; necessary to ensure enough pressure reaches the nozzle.
• C. Temperature rise in the line; to estimate nozzle temperature.
• D. Crew fatigue due to hose handling; to plan breaks.

Answer: (B)

Friction loss is the pressure drop that occurs as water flows through hose, fittings, valves, and other piping. In firefighting, you calculate this loss to know how much pressure is needed at the pump to deliver the required nozzle pressure at the end of the line. The pump discharge pressure must overcome friction losses (and any elevation or appliance losses) so the nozzle receives sufficient pressure for an effective stream. If friction loss isn’t considered, you may end up with too little pressure at the nozzle, resulting in a weak flow and poorer reach. Friction loss increases with higher flow and longer hose, and larger-diameter hose reduces it, which is why hydrants, hose layouts, and hose sizes are planned with these calculations in mind.