PURPOSE: To allow a pump body to be inserted into and joined automatically to a pump casing when the pump body is dropped and to make electric connection detachably on the upper surface of a pump cover by enabling the pump body to move vertically with a suitable guide means.

CONSTITUTION: When it is attached or detached, the pump body only is hung with a hanging chain 13 from an upper opening part 22 of a tank and dropped toward the pump casing 16 under the engagement of a guide tube 14 with a recess 1a. The pump body is centered and supported at the falling end through lower guide vanes 5a and the lower inner surface of the pump casing 16. At the same time, the center of the pump is adjusted through the engagement of a vertical guide part 1b of a pump cover metal 1 with the inner edge of the opening part of the casing 16, the pump body is sealed watertightly and supported by an O ring 21, further, antiswivelled by corrugations 16c, 16c also and can be connected automatically to the casing. The electric connection part between a motor part 3 and cable parts 12 can be detected easily by mere attaching and detaching of one cover metal 1 on the side of the vertically movable pump body.