upgrading existing plants the wash press forms the pulp web 21 between the perforated and dewatered outer surface of the drum 2 a 2 b and the surrounding trough sweep of which a first section consists of pivotable trough sweeps 10 a 10 b and a final sweep section consists of a raisable and lowerable trough base 11 the first sections can have weakly converging trough sweeps with one or more wash liquid distributors 12 arranged transverse to the pulp web each distributor housing 3 a 3 b for each drum comprises a feed screw 4 a 4 b arranged in the cylindrical distributor housing with its cylinder axis arranged horizontally and transverse to the pulp web 21 fig2 shows one distributor housing seen from above in fig1 the feed screw 4 a 4 b is provided with a screw thread 15 with a substantially constant pitch and a screw core 14 with a continuously increasing core diameter as seen from the inlet 6 a 6 b corresponding to that shown in se c 448009 the distributor housing can as is shown in se c 448009 have an inlet at one end of the distributor housing but in fig2 the inlet is arranged at the middle of the distributor housing and the screw thread 15 of the feed screw is mirror inverted as seen from the centre of the inlet for conveying the pulp out towards the end walls of the distributor housing in this way it is possible to obtain a uniform.