The device for producing ultrapure water according to the reverse osmosis principle with a reverse osmosis filter which is subdivided by the RO membrane into a primary chamber and a secondary chamber, with a primary circuit through which raw water is supplied to the primary chamber and concentrate is discharged therefrom, and with a secondary circuit for supplying permeate to at least one consumer, preferably to a dialysis device, is characterized in that a means for detecting organic and/or inorganic deposits is arranged in or on the primary circuit and/or the secondary circuit and is connected to an evaluation means.