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 (4, 7) 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 (4, 7), in which the variable (I_ist) is the current (I_ist) consumed by the pump assembly (4, 7) and/or a variable dependent thereon, and in which a table is stored in the pump assembly (4, 7) 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 (4, 7) 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 (4, 7) 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 (4, 7) 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 (4, 7) 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 (4, 7) 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 (4, 7) 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 (4, 7) 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 (4, 7) 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 (4, 7) 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 (4, 7) 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)).