System separator having a housing defining an inlet chamber, an intermediate chamber and an outlet chamber, having backflow preventers positioned in the housing and connected one after another in the flow direction of a medium, specifically a first, inlet-side backflow preventer connected between the inlet chamber and the intermediate chamber, and a second, outletside backflow preventer connected between the intermediate chamber and the outlet chamber, and having an outlet valve venting the intermediate chamber between the backflow preventers, which is controlled on the basis of a differential pressure between the pressure in the inlet chamber and the pressure in the intermediate chamber, each backflow preventer comprising a nozzle body, a valve disc and a spring element, the nozzle body of each backflow preventer having, radially on the outside, an annular circumferential projection which projects into an annular groove of the housing that is interrupted at one circumferential position and which is secured in the groove via at least one securing element, and an annular securing element that is plate-like in cross section and is divided at one circumferential position being positioned in the region of each backflow preventer, between the respective annularly circumferential projection of the respective nozzle body and a wall delimiting the respective groove of the housing with respect to the intermediate chamber, characterized in that to thread the securing element into the groove between the projection of the nozzle body and the wall delimiting the groove with respect to the intermediate chamber, the respective securing element can be bent up axially, namely by means of axially forcing apart ends (27, 28) of the securing element that are formed by the circumferential division, wherein one of the ends (27, 28) bent up by being axially forced apart can be threaded into the groove, wherein, by means of subsequent rotation of the securing element about an axis extending in the axial direction of the same, the same can be threaded completely into the groove. having a housing defining an inlet chamber, an intermediate chamber and an outlet chamber, having backflow preventers positioned in the housing and connected one after another in the flow direction of a medium, specifically a first, inlet-side backflow preventer connected between the inlet chamber and the intermediate chamber, and a second, outletside backflow preventer connected between the intermediate chamber and the outlet chamber, and having an outlet valve venting the intermediate chamber between the backflow preventers, which is controlled on the basis of a differential pressure between the pressure in the inlet chamber and the pressure in the intermediate chamber, each backflow preventer comprising a nozzle body, a valve disc and a spring element, the nozzle body of each backflow preventer having, radially on the outside, an annular circumferential projection which projects into an annular groove of the housing that is interrupted at one circumferential position and which is secured in the groove via at least one securing element, and an annular securing element that is plate-like in cross section and is divided at one circumferential position being positioned in the region of each backflow preventer, between the respective annularly circumferential projection of the respective nozzle body and a wall delimiting the respective groove of the housing with respect to the intermediate chamber, characterized in that to thread the securing element into the groove between the projection of the nozzle body and the wall delimiting the groove with respect to the intermediate chamber, the respective securing element can be bent up axially, namely by means of axially forcing apart ends (27, 28) of the securing element that are formed by the circumferential division, wherein one of the ends (27, 28) bent up by being axially forced apart can be threaded into the groove, wherein, by means of subsequent rotation of the securing element about an axis extending in the axial direction of the same, the same can be threaded completely into the groove.