PURPOSE: To avoid the mixing of different liquids and to enhance a transported liquid quality by providing a recovery line at an outlet section of a pump to recover a residual liquid which often remains at the lowest part of a tank.

CONSTITUTION: An evacuation outlet 11 which exists at one end of an drain cock 10 which is provided at the bottom of a tank 1 and an evacuation pump 5 is connected with a recovery line 12. When an unloading work is over, the dump 5 is stopped and the drain cock 10 is closed at the same time. Thereafter, if the dump 5 is driven again at a low-speed, the air will be compressed into the piping to become a compressed air therein, and owing to its pressure force, a residual liquid inside the evacuation pump and its surrounding pipings gets evacuated through the recovery line 12.