A rotary multi-port valve having a valve body defining a valve chamber and having a plurality of inlet flow ports each having a stationary seat member therein and having a discharge port. A flow diverter member is supported by a valve stem and a tubular trunnion for rotation within the valve chamber and has a diverter chamber. A piston is hydraulically moveable within the diverter chamber and has driving connection with a diverter valve member is linearly moveable for sealing engagement with a selected stationary seat member. The diverter valve member is selectively retracted to a position completely within the valve chamber to permit selective rotation of the flow diverter member within the valve body to an aligned position with any of the inlet ports of the valve body.