This section describes the use of the group in the drainage system, forward, gravity filtration, with its water area of ??water, siphon head in backwash. Therefore there are no filters like high-speed, medium-speed filter, mechanical filter, as well as ordinary fast filter backwash pump goods must be set backwash water tower. The filter tank, used more with the number of red water pipe, and arranged at their respective area centroid axis of the graph. Therefore backwash water distribution uniformity of water after its water and then filtered water district uses stomping sump to collect, so after the filter tank in place, the extent of the sump level crest of adaptability, which can even catchment. Filter products in larger size, compared with the national plotting reinforced concrete gravity-free valve filter, increasing the Meizu three type series (ie, when a filter backwash tank filter supplied by the same group of three anti- rinse water) Final head loss control value is also the country's largest plotting 1.5m and 1.9m 1.7m adds two grades, elevation arranged waterworks designed to provide a convenient choice of products.