Abstract: There is disclosed a method of filtering liquids in a vertical tower filter tank with a flat bottom and liquid inlet and outlet means for flowing liquid under pressure into a sand filter column in the tower tank causing the liquid to flow through distribution gaps which direct the flow horizontally through the filter into a collection pipe and upward out the outlet. In addition the filter is regenerated by backflowing washwater under pressure so the filter grains are slurried and the impurities are removed therefrom and washed out an overflow outlet. The apparatus for conducting the filtering and regeneration are also disclosed. The apparatus has a flat bottom and at least one perforated wall to divide the filter column into sections. There is an inlet for the washwater having a speed accelerating throat.