What term describes an appliance that has an inlet and outlet of matching size and steals water from the main line?

The term that describes an appliance with an inlet and outlet of matching size that diverts water from the main line is known as a water thief. This device is specifically designed for situations where multiple lines need to be supplied with water simultaneously from a single water source or main line without compromising the flow or pressure in the system.

The water thief allows for the connection of multiple hoses or devices and effectively "steals" or diverts a portion of the main water flow while maintaining its pressure and volume to other downstream users. This makes it particularly useful in fire suppression scenarios where multiple hoses may be needed to combat a fire efficiently.

Understanding the role of a water thief is essential in firefighting operations, as it enables firefighters to effectively distribute water from a single source to multiple areas, enhancing their capability to control and extinguish fires rapidly.