A precoat filter element for a precoat filter unit comprises a flow distributor and flow straightener. The flow distributor surrounds a filter septum and has openings through which liquid may flow. The proportion between the area of openings and the area of a wall of the flow distributor may vary along the length of the septum to distribute flow over the length of the filter septum in a predetermined manner. A flow straightener is provided at the base of the septum to reduce turbulence during precoat and filtration operations, and to reduce the occurrence of large flocs in precoat slurries during coating operations.