PURPOSE: To eliminate the needs to regulate the opening degree of valves during the discharge of a treating liquid and prevent the transfer of sludge by providing a float supported in a vertically movable way in the inside of a tank and attaching the tip of a flexible discharge pipe to said float.

CONSTITUTION: In a set ring tank 30 provided with the discharger 40, a treating liquid in the tank 12 is stored through the forward pipe 34 and the inlet pipe 31 by the pump 26 during the downtime period. During the period, the float 40a rises with the surface of the treating liquid ascending inside the tank 30 while extending the discharge pipe 40b and stops when reaching the upper stopper 38. On the other hand, at the time of restart of treating operation, the treating liquid in the tank 30 flows into the discharge pipe 40b through the funnel 42 opening below the float 41 and then sent to the treating liquid tank 12 through the discharge pipe 32 and the return pipe 35.