A rotary flow valve apparatus and associated systems and methods, comprising: a front plate (11) comprising a plurality of fluid entry ports (14) running therethrough; a rear plate (12) comprising one central fluid exit port (30) running through a substantial center thereof and P peripheral fluid exit ports (31-36) running through a substantially circumferential periphery thereof; P flow selector bars (91) integrally connecting the front plate (11) with the rear plate (12) and fixing the front plate relative to the rear plate; P inter-bar flow channels (92) defined between rotationally-adjacent pairs of the flow selector bars (91); and a selector cylinder (13) seated over and freely and continuously rotatable around the flow selector bars and relative to the front and rear plates.There are twice as many entry ports (14) as peripheral exit ports (31-36). When peripheral flow channel (62) aligns with two such ports, flow to central exit port (30) is blocked by a selector bar (91) and fluid exits only through the selected peripheral exit port. When the peripheral flow channel (62) aligns with a blank on plate (12) radially aligned with a flow channel (92), flow is allowed through channel (92) and fluid exits only through the central exit port (30). When the peripheral flow channel (62) is in an intermediate position fluid exits through both a peripheral exit port and the central exit port.