A system for controlling fluid flow through i lines, wherein the i lines are connectable through tubing to i zones, respectively, and wherein i=1, 2, . . . , N. The system includes at least one valve and a pressure transducer in each of the i lines, a control device for controlling the valves, and a zone pressure estimator. The zone pressure estimator is connected to the pressure transducers and is programmed to calculate an estimated pressure in each the i zones and provide the estimated pressures to the control device.