The rotary drum vacuum filters are composed by a horizontal cylindrical drum divided into sections connected by means of pipes, to a distribution valve. The drum, covered by a filtering cloth in in polypropilene or other synthetic material lying on drainage grids manufactured by in polypropilene or different materials, rotates, at variable speed, partially immerged in a tank equipped with agitator in order to maintain in supension the slurry to be filtered. During rotation the drum is divided in four separate areas by means of the bridges foreseen inside the valve, that are : filtration area corresponding to the submerged part of the drum, washing area, drying area and cake discharge area.