Abstract: A filtration tank and means for subsequent purification of filter bag purified waste water, especially grey water, which is introduced into the top of a filter tank and is evenly distributed by means of spray nozzles on the top layer of purification media, which are built up in layers in a tank around a built-in central pipe. The layers of purification media consist of varying types of material and grain size, density, weight, ect. The water passes through the varying layers of purification medium and is collected on the bottom of the central pipe, where a pump lifts the water through a U.V. treatment apparatus for sanitation.