Filtering 

Here comes to the primary function of the filter tank. After the process of precipitation, it purifies the water once more through the fine sand filtration method toward the fine particles that have not been completely removed in the filtration process. After completion of such a process, the clean water will be distributed from the filter well onto the second pump well or onto the water purification tank for water distribution.

Each and every filter tank is equipped with a filter well to adjust the water supply process. On the both sides of a filter tank, there would be a sand storage and sand washing field to store the fine sand for filtering purposes. With use of the cross-shaped tunnel-type tiles, we would form a slope shape with fine sand to be applied onto the top while a rectangular ditch is left in the center of the pool to collect the clear water filtered with the bricks and sand. Where the collection process takes as long as up to 4 to 7 days, it is called a slow filter pool. The water so filtered is in a quality far better than that filtered with a quick filter and is more significantly better oriented to human drinking purposes.

A fast filter is in fact a filter bed made of anthracite, filter sand, gravel and the like stacked in layers according to the particle sizes. After the filter layer is used for a period of time, impurities tend to accumulate and would, in turn, diminish the filtering effect. It would call for the so-called "backwash sand" operation. With use of strong water pressure upward to flush the filter materials with clean water from the bottom of the filter tank so as to remove impurities out of the filter layer. Through such an elaborate process, we firmly ensure a flawless filtering effect.