A pulp-filter arrangement (1) comprises a rotatable drum (10) and a non-rotating valve arrangement (30). The rotatable drum (10) has a cylindrical water-permeable pulp-supporting shell (14), a plurality of drain pipes (16) and a rotating hollow shaft (18). The plurality of drainpipes (16) connects the rotating hollow shaft (18) with a collecting channel (22) situated radially directly inside the cylindrical water-permeable pulp-supporting shell (14). The non-rotating valve arrangement (30) is disposed within the rotating hollow shaft (18) for sealing off the rotating hollow shaft (18) from a radially inner outlet (24) of the drain pipes (16) when respective radially inner outlet (24) is situated within a sealed zone. The non-rotating valve arrangement (30) is further arranged to, in a transition zone immediately following the sealed zone, open a throttled passage between the rotating hollow shaft (18) and the radially inner outlet (24).