Multimedia filters are designed for the purification of raw water with high content of suspended particulate matter, metal hydroxides and plankton. These devices are used for water clarification or as a pretreatment in the multi level purification system. In the flow from top to bottom, contaminants from the water are retained in the layer of the filter material. Fillings of the filters are usually made of quartz sand and gravel, expanded SiO2 and/or anthracite of different particle sizes.