Abstract: A method to clean a drum of a vacuum dryer including: rotating the drum about an axis in a first direction to form the cake of material on the drum as it moves through a vat of the material, wherein an outer layer of the cake is a precoat layer formed from the material in the vat; drawing filtrate through the cake and filter on the drum to a network of conduits in the drum, wherein the precoat layer thickens as the filtrate is removed: mechanically scraping at least a portion of the precoat layer from the cake; discharging a wash liquid from a row of nozzles of a wash structure, wherein the wash liquid is discharged in a sequence in which one of the nozzles in the row discharges the wash liquid while other nozzles in the row are not applying the wash liquid to the drum.