A filter system is provided with a housing provided with a cover. The housing has a raw liquid inlet, a clean liquid outlet, and a liquid drain. A filter element is provided that separates a raw side from a clean side. A slide valve with a valve rod and a sealing head is provided, wherein the sealing head is arranged such that the liquid drain of the housing is closable but openable. A coupling is arranged between the sealing head and the valve rod, providing an axial securing action of the valve rod at the sealing head and a radial securing action, separate from the axial securing action, of the valve rod at the sealing head. A slide valve for such a filter system as well as a sealing head and a valve rod for such a slide valve are provided.