Reuse of solvent startup/shutdown fluid for concentration control

A system to recycle waste ink for reuse as replenishment fluid is for an inkjet print station that includes a printhead with a fluid inlet and a fluid outlet. The system uses an ink supply tank, an external ink supply tank with fresh ink and an ink supply valve to control ink flow from the external ink supply tank to the ink supply tank. The system includes a replenishment fluid supply valve for controlling flow between a replenishment fluid supply and the ink supply tank, a device for monitoring ink concentration in communication with ink, a waste tank and a waste reuse valve for controlling flow between the waste tank and ink supply tank. The system includes level sensors and one or more controllers to control any valves, sensors, and pumps associated with the system to optimize operation of the system.