Final answer:
A Y connection is used in firefighting to split a single hose line into two, enabling connection to a hydrant or a nozzle, thereby increasing the efficiency and range of firefighting operations.
Step-by-step explanation:
A Y connection, also known as a wye or siamese connection, is an apparatus used in firefighting to split a single hose line into two separate lines. This allows firefighters to deploy more hoses and cover more area, or to have multiple teams work off the same water supply. The Y connection can indeed be used on fire lines to connect two lines of hose to a single hydrant, allowing for more efficient water delivery. Additionally, it can also be attached to a single nozzle to supply it with water from two hose lines. This type of connection is crucial for effective fire suppression as it increases the flexibility and range of the firefighting team. It is an essential component of the equipment carried by fire engines or used in fixed firefighting installations.