A washing station for washing flexographic plates with water-based washing liquid, wherein said washing station comprises an operative chamber and brushing means for brushing said plates, wherein said station comprises a treatment unit outside said chamber for treating a water-based washing liquid used in said washing station, wherein said liquid comprises some monomer or polymer detached from said plates during their washing, wherein said treatment unit comprises: - a first tank for collecting said washing liquid to a predetermined minimum filling level, said monomer or said polymer surfacing in said first tank after said liquid rests for a predetermined interval of time; - a second tank comprising a first inlet section arranged at a lower height than said minimum filling level of said first tank; - a third tank for collecting said washing liquid to a predetermined minimum filling level (L1*), said monomer or said polymer surfacing in said third tank after said liquid rests for a predetermined interval of time, wherein said second tank also comprises a second inlet section arranged at a lower height (H1*) than said minimum filling level (L1*) of said third tank; - first barrier means, movable between a closing position, in which said first barrier means prevent the communication between said first tank and said second tank and an opening position, by effect of which the first tank and the second tank become communicating so that at least said monomer or said polymer surfaced in said first tank can overflow into said second tank at said first inlet section, and - second barrier means, movable between a closing position, in which said second barrier means prevent the communication between said third tank and said second tank and an opening position, by effect of which the third tank and the second tank become communicating so that at least said monomer or said polymer surfaced in said third tank can overflow into said second tank at said second inlet section. - a first tank for collecting said washing liquid to a predetermined minimum filling level, said monomer or said polymer surfacing in said first tank after said liquid rests for a predetermined interval of time; - a second tank comprising a first inlet section arranged at a lower height than said minimum filling level of said first tank; - a third tank for collecting said washing liquid to a predetermined minimum filling level (L1*), said monomer or said polymer surfacing in said third tank after said liquid rests for a predetermined interval of time, wherein said second tank also comprises a second inlet section arranged at a lower height (H1*) than said minimum filling level (L1*) of said third tank; - first barrier means, movable between a closing position, in which said first barrier means prevent the communication between said first tank and said second tank and an opening position, by effect of which the first tank and the second tank become communicating so that at least said monomer or said polymer surfaced in said first tank can overflow into said second tank at said first inlet section, and - second barrier means, movable between a closing position, in which said second barrier means prevent the communication between said third tank and said second tank and an opening position, by effect of which the third tank and the second tank become communicating so that at least said monomer or said polymer surfaced in said third tank can overflow into said second tank at said second inlet section.