1. A hydrocyclone for separating a fiber suspension into a heavy fraction and including a distribution head for supplying a fluid to the separation chamber, which distribution head is situated centrally in the separation chamber relatively close to the other end. The distribution head has at least one outlet passage designed for spraying a fluid jet, the fluid jet having a flow component in the direction towards the other end of the separation chamber, and the fluid jet having another flow component directed towards the one end.