A system and method for dosing at least two concentrates into water for on-line preparation of a medical fluid may include a main line for feeding of water, a first line with a first pump for feeding a first concentrate into the main line at a first mixing point, a second line with a second pump for feeding a second concentrate into the main line at a second mixing point, wherein a main concentration sensor measures the concentration in the main line downstream of the first and the second mixing points, wherein control of the dosing of the first concentrate is initially under feedback control from the main concentration sensor to the first pump, and when a value for a feeding parameter for the first pump is determined the feedback control is moved, so that the value for the feeding parameter is used to control the first pump.
