Which set of factors most influence friction loss in a hoseline?

• A. Hose color
• B. Water temperature
• C. Hose size, length, flow rate (GPM), and number of fittings/elbows
• D. Altitude and barometric pressure

Answer: (C)

Friction loss in a hoseline comes mainly from how water moves through the hose and fittings. The diameter of the hose affects how easily water can flow; a larger size reduces resistance, while a smaller size increases velocity and friction per unit length. The longer the hose run, the more surface the water has to rub against, so pressure drops rise with length. Flow rate (GPM) matters because higher flow means more turbulence and energy is lost fighting the walls, roughly increasing with the amount of flow for a given hose size. Fittings and elbows disrupt smooth flow, adding additional loss each time water changes direction.

Hose color has no impact on friction loss, and water temperature only has a minor effect on viscosity that isn’t significant in typical firefighting scenarios. Altitude and barometric pressure don’t materially change friction loss in a standard hose line. So the factors that truly drive friction loss are hose size, length, flow rate, and the number of fittings/elbows.