The invention relates to a dirt precipitator (100) for a highly viscous medium, having a housing comprising a front housing element (30; 30′) that comprises at least one inlet channel (33) and a rear housing element (20) that comprises at least one outlet channel (23), and having a screen wheel (10; 10′) rotatably mounted between the housing elements (20, 30; 30′) having a number n of screen positions disposed in a ring zone, on each of which at least one screen opening (11.1, . . . , 11.12) having at least one screen insert element is provided. The inlet channel (33), the outlet channel (23), and the screen opening (11.1, . . . , 11.12) are disposed flush one after the other in at least one working position and form a flow channel. In all positions of the screen wheel (10; 10′), more than 50% of the screen openings (11.1, . . . , 11.12) are always able to be permeated, and are impinged by flow from at least one inlet channel and from which at least one outlet channel leads.