Which of the following is not typically a factor in estimating safe water supply duration?

• A. Nozzle pressure, friction loss, hose length, pump discharge, and duration until flow is achieved.
• B. Ambient weather conditions during suppression.
• C. Occupant load and building height.
• D. Distance to water source and hydrant availability.

Answer: (C)

Estimating safe water supply duration is about how the water actually moves and lasts in the system, not about how many people are inside the building. The main idea is to account for the hydraulics and logistics: what pressure you need at the nozzle, how much friction loss occurs along the hoses, the length and diameter of the hose lay, the pump’s discharge capacity, and how long it takes to get water flowing. All of these determine how much water you can deliver over a period of time.

Occupant load and building height don’t set the length of time the supply can continue once you’re delivering water. They influence how much water you might need overall and where you must push water (for example, higher floors requiring more pressure), but they don’t define the duration your system can sustain flow given a fixed source and hose setup. That’s why this factor is not typically used when estimating safe water supply duration.

Distance to the water source and hydrant availability directly affect how quickly you can establish a supply, and ambient weather can influence conditions on scene, but the core duration calculation rests on the hydraulics and source capacity.