A system for regulating the balanced flow of fluids, comprising: first and second fluid channels (149, 156) each with a respective pump (132, 140, 434, 436) for each of said first and second fluid channels, a controller (50, 166, 466, 766) connected to the respective pumps to control the rate of pumping of one or more of said respective pumps, the controller being connected to one or more valves (134, 136, 432, 430) to permit it to establish flows in the first and second channels of equal volume flow rate responsively to calibration data stored in said controller; the first and second channels (149, 156) having pressure sensors (126, 141) positioned to measure a local pressure upstream of at least one of said respective pumps; the first and second channels (149, 156) connecting to a fluid handling device (120,402) in which a ratio of flow rates of entering and leaving flows to and from said fluid handling device is maintained by said controller; a test flow branch (120, 320, 402) connecting the first channel to said second channel through the one or more valves, the test flow branch having a pressure sensor; the controller (50, 166, 466) being configured to, at selected times, temporarily establish a flow from said first channel to said second channel through the test flow branch (320,402,154,441)and to sample a signal of a test branch pressure in said test branch at said controller; the controller being configured to, in response to said samples, adjust said calibration data stored in said controller (50,166,466); and the controller (50,166,466) being configured to adjust the one or more of said respective pumps (132, 140, 434, 436) using the adjusted calibration data stored in said controller (50, 166, 466), wherein said controller is connected to receive the local pressure, said adjusting being responsive to both said test branch pressure signal and said local pressure signal. first and second fluid channels (149, 156) each with a respective pump (132, 140, 434, 436) for each of said first and second fluid channels, a controller (50, 166, 466, 766) connected to the respective pumps to control the rate of pumping of one or more of said respective pumps, the controller being connected to one or more valves (134, 136, 432, 430) to permit it to establish flows in the first and second channels of equal volume flow rate responsively to calibration data stored in said controller; the first and second channels (149, 156) having pressure sensors (126, 141) positioned to measure a local pressure upstream of at least one of said respective pumps; the first and second channels (149, 156) connecting to a fluid handling device (120,402) in which a ratio of flow rates of entering and leaving flows to and from said fluid handling device is maintained by said controller; a test flow branch (120, 320, 402) connecting the first channel to said second channel through the one or more valves, the test flow branch having a pressure sensor; the controller (50, 166, 466) being configured to, at selected times, temporarily establish a flow from said first channel to said second channel through the test flow branch (320,402,154,441)and to sample a signal of a test branch pressure in said test branch at said controller; the controller being configured to, in response to said samples, adjust said calibration data stored in said controller (50,166,466); and the controller (50,166,466) being configured to adjust the one or more of said respective pumps (132, 140, 434, 436) using the adjusted calibration data stored in said controller (50, 166, 466), wherein said controller is connected to receive the local pressure, said adjusting being responsive to both said test branch pressure signal and said local pressure signal.