Sand filter

摘要

A liquid filter has an annular layer of sand which is arranged between interior and exterior separation walls. The sand bed formed in this manner is arranged in a vertical container, the top side of which is closed. The bottom end of the annular sand layer surrounds an outlet. A pillar having a vertical orifice designed as a slotted nozzle is rotatably arranged around the outlet so that it rotates on backwashing the filter and sprays liquid against the sand layer.