The invention relates to a device for filtering liquids, comprising parallel planar membrane pockets and means for pressure-tight connection of the membrane pockets and for coupling of a suction. The membrane pockets contain a drainage element with a planar connection to two membranes which is pressure-tight around the edges. Adjacent membrane pockets are connected together and to the suction by means of one or more drain drillings and corresponding lines. The drain drillings are so arranged that the trans-membrane pressure difference falls only slightly across the area of the membrane pocket.
