Filter System, Filter, and Method

A filter system for liquid has a filter head with drainage channel and stop element. A filter cartridge is mounted by screw-in movement at the filter head and has a support ring rotatably fastened to its housing part. The support ring has an eccentric closure element and a first positioning element guided toward the stop element by the screw-in movement to position the support ring at the filter head in a rotational position for axially aligning closure element and drainage channel. The closure element is transferred axially into a sealing seat at the filter head to close the drainage channel when screwing on the filter cartridge. The support ring has a second positioning element holding the support ring in a rotationally fixed position at the filter head when unscrewing the filter cartridge so that the closure element is moved out of the sealing seat only in an axial direction.