Apparatus configured to control chamber pressure during pipette rinsing having lower pressure recovery time. Pressure control apparatus includes pipettes to dispense liquid, a manifold chamber to supply liquid to the pipettes, a flow control valve in each flow path, a pump to supply the liquid, a pressure sensor to provide measured pressure, and a flow controller, which in a calibration mode, decreases a pump drive setting if measured pressure is high, increases the setting if measured pressure is low, and stores the pump drive setting for the individual combined operational state if the pressure is within predetermined pressure threshold limits, or in a testing mode, determines if the measured pressure is within the threshold limits for a previously-commanded state combination, and adjusts the pump drive setting if not within the threshold limits for a next time. Methods for operating pressure control apparatus are described, as are other aspects.