DIALYZER

The invention relates to a filter device for the exchange of substances, comprising a pipe section-shaped housing with a center of gravity and with two housing ends, in which housing a hollow fiber bundle consisting of semi-permeable membranes is arranged, comprising, furthermore, an end cap having a first and second opening, wherein the housing and the end cap configure a first sealing surface which connects the housing and the end cap sealingly, and wherein the first sealing surface is spaced apart further from the center of gravity of the housing than the aperture, and wherein a first fluid chamber is formed between the first sealing surface and the first opening of the end cap, via which first fluid chamber the first opening is connected to the first flow chamber, wherein the housing and the one end cap configure a second sealing surface, wherein the first and second sealing surface are not configured by way of a sealant.