Which of the following sizes are considered supply lines in firefighting?

Supply lines are critical in firefighting as they transport large volumes of water from a water supply source to the fire scene. The size of the supply line directly affects its ability to deliver sufficient water flow for firefighting operations.

The sizes classified as supply lines, notably the larger diameters like 2.5 inches and above—such as 3 inch, 4 inch, 5 inch, and 6 inch—allow for a higher volume of water to be moved at lower friction loss, making them effective for supplying the necessary amounts of water for extinguishing fires. These larger lines are essential when the fire demands significant water flow, which is often the case in urban fire scenarios or larger structural fires.

In contrast, smaller hoses, such as those measuring 1 inch, 1.5 inch, or 2 inch, are typically used for attack lines, where the focus is on delivering water more precisely to the point of the fire rather than for supplying large quantities of water. Attack lines are generally employed to extinguish fires once a quality supply line setup is in place. Therefore, choosing the larger diameter hoses as supply lines is essential for effective firefighting operations.