Procedure for operating a pump assembly, notably for a lifting system for delivering a liquid by means of a pressure line to a collecting line , where the pump assembly automatically sets a setpoint volume flow (Q SOLL ) specified for it from a plurality of specifiable setpoint volume flows on the basis of a physical variable (I_ist) of the pump assembly , in which the variable (I_ist) is the current (I_ist) consumed by the pump assembly and/or a variable dependent thereon, and in which a table is stored in the pump assembly that assigns a value (I(n_i, Q)) of the variable to a plurality of discrete rotational speeds (n_i) for each specifiable setpoint volume flow (Q Soll ), said variable corresponding to a certain operating point (H IST , Q IST ) of the pump assembly determined by the corresponding rotational speed (n_i) and the corresponding setpoint volume flow (Q Soll , with the volume flow (Q IST of the pump assembly being adjusted on the basis of this table by adjusting the rotational speed so that the variable (I_ist) substantially corresponds to a specific value (I(n_i, Q Soll )) assigned to the specified setpoint volume flow (Q SOLL ), characterised by the procedure encompassing the following steps: a Operation of the pump assembly at a first rotational speed (n_i) b Determination of the current value of the variable (I_ist) c Comparison of the value (I_ist) with a value (I(n_i, Q Soll )) of the variable assigned to the setpoint volume flow (Q Soll ) at the first rotational speed (n_i) in which, depending on this comparison, i the rotational speed (n_i) of the pump assembly is increased to a second rotational speed (n_i+1) when the current value of the variable (I_ist) does not substantially correspond to the value of the aforesaid assigned value of the variable (I(n_i, Q Soll )), and the steps a, b and c are repeated subject to the requirement that the value of the first rotational speed (n_i) corresponds to the value of the second rotational speed (n_i+1), or ii the set rotational speed (n_i) of the pump assembly is maintained when the current value of the variable (I_ist) substantially corresponds to the assigned value of the variable (I(n_i, Q Soll )). a Operation of the pump assembly at a first rotational speed (n_i) b Determination of the current value of the variable (I_ist) c Comparison of the value (I_ist) with a value (I(n_i, Q Soll )) of the variable assigned to the setpoint volume flow (Q Soll ) at the first rotational speed (n_i) in which, depending on this comparison, i the rotational speed (n_i) of the pump assembly is increased to a second rotational speed (n_i+1) when the current value of the variable (I_ist) does not substantially correspond to the value of the aforesaid assigned value of the variable (I(n_i, Q Soll )), and the steps a, b and c are repeated subject to the requirement that the value of the first rotational speed (n_i) corresponds to the value of the second rotational speed (n_i+1), or ii the set rotational speed (n_i) of the pump assembly is maintained when the current value of the variable (I_ist) substantially corresponds to the assigned value of the variable (I(n_i, Q Soll )). i the rotational speed (n_i) of the pump assembly is increased to a second rotational speed (n_i+1) when the current value of the variable (I_ist) does not substantially correspond to the value of the aforesaid assigned value of the variable (I(n_i, Q Soll )), and the steps a, b and c are repeated subject to the requirement that the value of the first rotational speed (n_i) corresponds to the value of the second rotational speed (n_i+1), or ii the set rotational speed (n_i) of the pump assembly is maintained when the current value of the variable (I_ist) substantially corresponds to the assigned value of the variable (I(n_i, Q Soll )). <EOS>