Ball tap

A ball tap constituted so as to keep a water level inside a water receiving tank at a water level set in advance by providing a valving element linked to a lever rod that swings vertically according to the water level inside the water receiving tank in a manner enabling the valving element to seat on and separate from a valve seat provided on a secondary side opening end face of a valve orifice opened on the same axis at that of a secondary side flow passage provided vertically inside a valve body, wherein the valving element includes a valve part provided with a contact projection part that can come into close contact with the valve seat when the valving element is closed, and a flange part having a circular ring shape in plan view which continues downward from the rim of the valve part and is slidable like a piston in the secondary side flow passage, and the left and right half circumferences of the upper surface of the flange part have bilaterally symmetrical shapes curved downward in arch shapes, and the left and right lower limit portions of the upper surface of the flange part are set so as to be positioned at the same heights as those of the lower end edges of drainage ports formed to expand on the left and right of the secondary side flow passage or slightly higher than the lower end edges when the valving element is fully opened.