A water filtering tank comprising a housing of the water filtering tank, water inlet pipe (3) installed on the housing receiving water into the tank, water distributing sheet (2) in which the said sheet is arranged inside the tank at the height lower than the inlet pipe (3) in which the said distributing sheet receives water flow through the inlet and comprises a plurality of pores positioned throughout the said sheet, rough filtering basket (1) in which the supporting lower surface comprises a plurality of pores and the said basket comprises rough filtering materials inside which arranged in the basket at the height less than the distributing sheet (2) and receives water flow through the said water distributing sheet, filtering material basket which is arranged inside the basket at the height less than that of the rough filtering basket (1) and comprises the filtering materials arranged into multiple layers and water outlet pipe (7) installed with the housing and releases water. Characterized in that the water filtering basket comprises a siphon tube supporting base (6) which is arranged at the lower part of the housing and further comprises a water outlet standing pipe (8) vertically installed on the said base and has the height less than the height of the inlet in which water is sucked out of the housing through the lower water outlet standing pipe (8) connected with the water outlet pipe (7) when water level filled inside the housing is at the same level as that of the water outlet standing pipe (8), siphon tube (10) covering the water outlet standing pipe (8) and further comprises snock tube (11) in which is in the U-shape having one end connected with the siphon tube at the predetermined height.