USAF Mobile Water Supply (MWS) Fire Practice Test

Increasing hose diameter lowers friction loss for the same flow. The reason is that a larger diameter means water travels slower (velocity falls as area grows), and friction loss depends strongly on velocity (it scales with velocity squared). With a bigger diameter, the velocity drops, so the friction losses per unit length decrease, reducing the total force required to push the water through the hose. This is why using larger hoses reduces pressure drop over a given run and helps maintain nozzle pressure while delivering the desired flow.