What hose appliance is used to split one hose into two or more separate lines?

A wye is a hose appliance specifically designed to split a single hose line into two separate lines, allowing multiple outlets for water flow. This function is particularly useful during firefighting operations when additional water streams are needed from a single supply line to cover different areas simultaneously or to provide water to multiple firefighting teams. The design of the wye typically features a single inlet to connect to a hose and two or more outlets, facilitating the easy distribution of water.

While the other options serve different purposes in fireground operations, they do not specifically function to split a single hose into multiple lines. A tree is generally considered a more complex branching system that facilitates multiple connections but lacks the straightforward simplicity of the wye. A manifold can also allow for multiple connections, often used in larger supply lines, but it serves a broader purpose and may not necessarily split a hose directly. A relay is used in tandem pumping operations to transfer water over long distances between two or more engines, rather than dividing a single line into multiple, smaller lines.