A rotary disc valve is used in a fluid delivery system to control flow of fluid between multiple ports of a valve housing. The valve housing may include a valve body and a lid that closes an open end of the valve body. In addition, the valve may include a diverter and seal assembly that are disposed in the valve housing. The diverter is configured to rotate about a rotational axis and to control fluid flow through the valve housing. The seal assembly provides a dynamic seal that is fluid tight within a plane that is perpendicular to the rotational axis. The diverter, the valve body and the seal assembly cooperate to define a fluid passageway that is coaxial with the rotational axis and passes through the seal assembly.