The present invention relates to an apparatus for determining the static patient pressure, wherein the apparatus comprises a pump in communication with a patient line for conveying a dialysis solution into the abdomen of the patient, and blocking means, in particular a valve by which the patient line is blockable, wherein the apparatus has a pressure chamber that is in fluid communication with the patient line with an open blocking element, with a pressure measurement device furthermore being provided that is arranged such that it measures the pressure in the pressure chamber or a pressure correlated with it; and wherein the apparatus comprises a control unit that is configured such that it effects a pressure build-up in the pressure chamber to a measurement pressure in a first step and opens the blocking element in a second step so that the patient line or a part section thereof is acted on by the measurement pressure of the pressure chamber and with the apparatus having an evaluation unit that evaluates the measured pressure after the opening of the blocking element.