Either single or dual grade sand is filled up in the top-open filter boxes. Under the filter media, the filter box is fitted with inlet distributor and a bottom collecting system. Externally, it is fitted with isolation valves and backwash water collection system. Pebbles and gravels are provided as the bottom layer under the sand bed of uniform size to support the sand bed. This filter removes mainly suspended impurities from the water source. Suspended impurities get trapped within the sand media when water having suspended impurities is passed through the sand bed and clear water comes out as the product. Backwash of the filter is to be carried out to remove these entrapped impurities from the filter, once it reaches to its maximum limits. This limit is governed by differential pressure across the filter.