What class of standpipes can accommodate hoses of different diameters using reducing valves?

Class III standpipes are designed to accommodate hoses of different diameters, allowing for the use of both 2½-inch and 1½-inch hoses. This flexibility is crucial in firefighting operations since different situations may require varying sizes of hoses to ensure effective water delivery. The reducing valves installed in Class III systems facilitate this adaptability, enabling the connection of hoses with different diameters to the same standpipe system.

In contrast, Class I standpipes are primarily intended for use by fire department personnel, offering a standard 2½-inch outlet. Class II standpipes are designed for use by occupants of the building or trained personnel and are equipped with 1½-inch hose connections, which are not compatible with larger hoses without additional equipment. The term "Wet Standpipe System" refers to the entire system being filled with water at all times, but it doesn't specifically address the functionality of accommodating different hose diameters, which is a defining feature of Class III systems.