A system for purifying a fibrous suspension consists of multiple hydro-cyclones arranged adjacent to one another in a row, each of the hydro-cyclones having at least one feed connection, one accepted stock connection and one reject material connection, and having at least one supply manifold which is connected to multiple feed connections and/or having at least one accepted stock manifold which is connected to multiple accepted stock connections and/or having at least one reject material manifold which is connected to multiple reject material connections, the manifold being elongated and the corresponding connections discharge at their longitudinal side into the corresponding manifold. At an end of at least one manifold which follows the final hydro-cyclone, a fluid or a suspension is guided via at least one flushing connection into or out of the manifold.