During wet screen the sandy water is drained to the trough. After the intake the bucket wheel lifts part of the watery sand immediately, the other part—the finer fractions— settle continuously in the trough. The spiral fixed to the shaft continuously pushes the settled sand towards the bucket wheel and then it is lifted with the buckets. The muddled water flows away from the trough through the waste-weir at the other end and gets into the muddled pipe. The frequency regulator built in the control ensures the equal loading of the sand washers as well as the optimal desiccation of the sand.