The sand filter is a filter that used one or several media as a filter material to remove suspended solids from water, which is beneficial for removing impurities in water. The system is equipped with perfect protection devices and monitoring instruments and has a backwash function, the dirt such as sludge and dirt are quickly washed away, and the water consumption is small. The automatic function can be set according to user requirements. Under certain pressure, the raw liquid passes through the medium to flocculate, absorb, and intercept, and remove impurities, thereby achieving the purpose of filtration. Normally, the filler material is quartz sand, anthracite, granular porous ceramics, manganese sand, etc., and users can choose to use it according to actual conditions. The filtration precision is between 0.005 and 0.01m, which can effectively remove colloidal particles and high molecular organic substances.