The swimming pool filters that make up the filtration system of a swimming pool are usually sand filters. The sand filters consist of a large tank, made of fiberglass, concrete or metal, which contains a thick layer of sand of a special quality, square in shape. During the filtering operation, the dirty water from the pool enters through the filter inlet pipe and leads it to the water distribution head located inside the tank.
While gravity causes water to pass through the sand, small particles of sand trap dirt and debris. At the bottom of the tank, the filtered water flows through the collection unit and exhausts it through the outlet pipe. Over time, dirt and debris collected in the sand slows down the flow of water. The pressure gauges at the entrance and the exit of swimming pool filters allow giving an idea of the level of internal blockage.
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If the pressure gauge shows a much higher pressure on the inlet tube than on the outlet tube, it means that there is a large amount of debris collected in the sand. This means that it is time to start a backwash of swimming pool filters. For backwash, you must adjust the number of valves to redirect the water flow. You must close the return pipe that leads the water to the pool and open the drain pipe, which lead to the sewer system.