Which factors influence friction loss in a hose line?

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

Answer: (C)

Friction loss in a hose line comes from the resistance water encounters as it travels inside the hose. The main factors that drive this loss are the hose’s size (diameter), the length of the hose, the flow rate (GPM), and how many fittings or elbows the water must pass through. A smaller diameter increases resistance because the water is forced through a tighter path, raising velocity and turbulence. A longer hose adds more surface contact and time for friction to act, accumulating greater pressure drop. Pushing more water through the line (higher GPM) speeds the water, which increases turbulent losses and hence friction. Each fitting or elbow creates a change in direction and flow area, adding extra resistance; the more fittings, the larger the overall friction loss.

Hose color has no impact on friction loss. Water temperature can slightly affect viscosity, but in typical firefighting ranges it’s negligible. Altitude can influence pump performance due to air pressure, but it doesn’t change the friction loss inside the hose itself. So the factors that truly determine friction loss are the hose size, length, flow rate, and the number of fittings/elbows.