PURPOSE: To facilitate the assemblage of a control circuit by providing a judging section for judging the establishment of requirement for permitting water supply at the water receiving tank side and a judging section for judging the establishment of requirement for water supply.

CONSTITUTION: A pump control unit PU is provide with a level detector for detecting the drought, full water, off-level and on-level in a water receiving tank 1 and an elevated tank 2. A requirement judgement control section judges the presence of establishment of the requirement for permitting water supply at the water receiving tank 1 side and the requirement for water supply from said tank 1 to the elevated tank 2 according to the detecting output of the level detector. When a change-over switch is changed over to the automatic side, two pump motors IM1, IM2 are run alternatively every time the requirement for the water supply is established.