Pump system, dialysis machine, and method of operating a pump

A method of conveying a dialysis solution with a pump system, said pump system comprising:

• a first piston pump and a second piston pump, each of the first piston pump and the second piston pump having a piston that cooperates with a working fluid which exerts a force on a conveying means that is a membrane, the first piston pump and the second piston pump being configured so as to operate in a staggered manner;
• setting means with which to, alternatively, reduce and increase, a conveying volume of the first piston pump and the second piston pump per piston stroke,
• the setting means including at least one of a piston stop to, alternatively, reduce and increase, the piston stroke, the piston stop being located in a piston chamber in which the piston moves, and
• means to, alternatively, reduce and increase, a quantity of the working fluid, the means to alternatively reduce and increase the quantity of the working fluid including a storage container for storing the working fluid, and a valve that enables a volume of the working fluid to alternatively be reduced and increased;
• calculation means with which to determine a residual desired conveying volume from a specific point in time onward;
• and
• input means or calculation means with which to input or determine a total desired conveying volume or a desired conveying volume per piston stroke, with the setting means being connected to the input means or to the calculation means with which to input or determine the total desired conveying volume or the desired conveying volume per piston stroke such that the setting means is configured to set the conveying volume of the first piston pump and the second piston pump per piston stroke in dependence on values input into the input means or determined by the calculation means with which to input or determine the total desired conveying volume or the desired conveying volume per piston stroke, said method comprising:
• alternatively, reducing and increasing the conveying volume per piston stroke to increase a conveying precision of the first piston pump and the second piston pump by at least one of changing the piston stop such that the piston stroke is alternatively reduced and increased, and, alternatively, reducing and increasing the quantity of the working fluid.