A 3 way valve is identified by its three:

A 3-way valve is specifically designed to control the flow of fluid through three distinct pathways or connections. These pathways allow the valve to either divert, mix, or cut off the flow of fluid, depending on its configuration and the position of the valve's internal mechanism. This ability to manage fluid direction is fundamental to the operation of hydraulic systems, which often require precise control over flow paths for effective functioning.

The configuration of a 3-way valve typically includes an arrangement that permits the connection of one port to two other ports, enabling it to either supply fluid to one of the two outlets or provide a return path. This is essential in various applications where flow direction or mixing of multiple sources must be managed.

In contrast, the other options do not accurately describe the defining characteristic of a 3-way valve. Seals are important for preventing leaks but do not define the valve's flow control capabilities. Spring mechanisms can be part of a valve but are not specific to 3-way valves. Lastly, while paths or pilot lines may relate to control systems, they do not pinpoint the functional design of the valve itself. Therefore, identifying a 3-way valve by its three ports succinctly captures its fundamental role in hydraulics.