An electrodialysis unit comprises a plurality of cathodes, a plurality of anodes and a plurality of membranes; the cathodes and anodes being arranged alternately in an electrode stack, with membranes in between each cathode and anode, anode flow paths formed between the membranes and anodes and cathode flow paths formed between the membranes and cathodes; the electrodialysis unit further comprising: an inlet manifold for distributing water to the anode flow paths or to the cathode flow paths, wherein the inlet manifold comprises a first tube provided with holes along its length, the holes being connected to the flow paths, and a second tube located within and enclosed by the first tube, the second tube having an inlet at one end and being closed at its second end and the second tube being provided with holes along its length that open into the first tube.