What must always be checked on a diverter valve to ensure proper flow?

The correct choice is the indicator, which is essential for ensuring that a diverter valve is functioning properly. The indicator provides visual feedback on the position of the valve, allowing operators to confirm whether the valve is open or closed, or if it is directing the flow as intended. This visual confirmation is crucial, as a diverter valve directs media between different paths in a system. If the valve is in the incorrect position, it could lead to improper flow, potential equipment damage, or system inefficiency.

While seals are also important for preventing leaks, they do not directly indicate whether the valve is functioning correctly in terms of flow direction. Similarly, a pressure gauge and a flow meter, while valuable for monitoring system performance, do not provide direct information about the valve's position. Therefore, relying on the indicator is essential for maintaining the correct operation of a diverter valve.