Filtration system comprising a seat element and a filter cartridge placeable on said seat element , the filter cartridge comprising a housing , the housing defining a top area and a bottom area and comprising an inlet and an outlet , the inlet and the outlet both being arranged in the bottom area , the housing further comprising a housing wall , an outer extension wall projecting downwards from the bottom area of the housing and providing a supporting edge , an inner extension wall projecting downwards from the bottom area of the housing and a snap-on rim being arranged in the bottom area and extending radially inwardly and, initially, axially downwards from the inner extension wall , the snap-on rim thereby defining a central axis Zc and encircling the outlet , the seat element having a bottom wall and a sealing seat defining a central axis Zs, the sealing seat protruding upwards from the bottom wall , the snap-on rim being arranged, upon being pushed over the sealing seat while the central axes Zc and Zs are aligned, to flip over from its initially axially downwards extending position into an axially upwards extending position, whereby the snap-on rim in the axially upwards extending position interacts with the sealing seat to create a sealing, characterized in that the filter cartridge and the seat element each comprise one of a pairing of positioning elements the positioning elements being arranged, upon being brought into contact with each other, to allow the snap-on rim to be pushed over the sealing seat only in a number of n defined rotational orientations, with respect to the central axis Zc, of the filter cartridge relative to the seat element . the filter cartridge comprising a housing , the housing defining a top area and a bottom area and comprising an inlet and an outlet , the inlet and the outlet both being arranged in the bottom area , the housing further comprising a housing wall , an outer extension wall projecting downwards from the bottom area of the housing and providing a supporting edge , an inner extension wall projecting downwards from the bottom area of the housing and a snap-on rim being arranged in the bottom area and extending radially inwardly and, initially, axially downwards from the inner extension wall , the snap-on rim thereby defining a central axis Zc and encircling the outlet , the seat element having a bottom wall and a sealing seat defining a central axis Zs, the sealing seat protruding upwards from the bottom wall , the snap-on rim being arranged, upon being pushed over the sealing seat while the central axes Zc and Zs are aligned, to flip over from its initially axially downwards extending position into an axially upwards extending position, whereby the snap-on rim in the axially upwards extending position interacts with the sealing seat to create a sealing, characterized in that the filter cartridge and the seat element each comprise one of a pairing of positioning elements the positioning elements being arranged, upon being brought into contact with each other, to allow the snap-on rim to be pushed over the sealing seat only in a number of n defined rotational orientations, with respect to the central axis Zc, of the filter cartridge relative to the seat element . <EOS>