What is the primary cause of resistance to flow in a hose line?

The primary cause of resistance to flow in a hose line is friction loss. When water flows through a hose, it experiences shear forces against the internal surfaces of the hose. This resistance is due to the roughness of the hose's interior, the length of the hose, and the flow rate. As the water moves, energy is consumed overcoming these internal frictional forces, leading to a reduction in pressure and flow rate at the discharge end of the hose.

Understanding friction loss is critical for fire officers and firefighters, as it directly affects the effective delivery of water to a fire. This concept helps them calculate appropriate hose lengths and nozzle pressures to ensure adequate water flow during firefighting operations. Therefore, knowing how to manage and account for friction loss is essential for effective fire suppression.