What is friction loss in a fire pump system?

• A. The pressure drop caused by water moving through hose, fittings, and appliances
• B. The pressure drop caused by water moving through hoses
• C. Pressure drop due to elevation difference
• D. The pressure at the nozzle only

Answer: (A)

Friction loss is the pressure drop that occurs as water moves through the system due to friction against the interior surfaces of hoses, pipes, fittings, and appliances. As water flows, turbulence and viscosity resist the motion, converting some of the pressure into heat. The amount of loss depends on the flow rate, the length and diameter of the hose or pipe, the roughness of the interior surfaces, and the number and type of fittings and appliances in the path. When you calculate pump discharge pressure, you add up all these friction losses along the route to the nozzle to ensure the desired nozzle pressure is achieved. Elevation changes create static pressure differences, and nozzle pressure is the pressure at the nozzle itself, so neither term represents the friction losses along the line. This description matches the option that describes the pressure drop caused by water moving through hose, fittings, and appliances.