Name three factors that determine whether to use a 1.75-inch vs 2.5-inch hose for exterior attack.

• A. Fire type, time of day, and hose brand.
• B. Required flow rate, distance to fire, and available water pressure.
• C. Weather, interior layout, and occupant load.
• D. Hose color, length, and manufacturer.

Answer: (B)

The main idea is that hose size for an exterior attack is chosen based on hydraulic needs: how much water you must deliver, how far that water has to travel, and what pressure your water source can provide. These three factors determine whether a 1.75-inch or a 2.5-inch hose is appropriate.

If you need a high flow to knock down the fire or protect a larger area, you’ll require more water at the nozzle. A larger-diameter hose can carry more water with less pressure loss over the same distance, so the 2.5-inch option becomes the better choice when the required flow is high.

Distance to the fire matters because longer lays incur more friction loss. The larger hose loses less pressure per length at a given flow, which helps you maintain the necessary nozzle pressure at the fire scene. For shorter distances with moderate flow, the lighter, more maneuverable smaller hose can be sufficient and easier to handle.

Available water pressure is the third pillar. If the supply pressure is limited, you must select a hose that will still deliver the needed nozzle pressure at the required distance. A larger diameter hose helps preserve nozzle pressure when pushing the same flow over a longer or more demanding run.

Weather, interior layout, occupant load, hose color, length, or manufacturer don’t directly set the hydraulic capability of the attack line, so they aren’t the primary factors in choosing between these hose sizes.