PURPOSE: To enable switchover to an optional water pressure and an optional water quantity by directly connecting a Wesco pump and a centrifugal pump to a normal/reverse rotation motor and independently providing suction ports and discharge ports respectively.

CONSTITUTION: A normally and reversely rotatable motor 1 is set so that its velocity control can be optionally carried out, and a centrifugal pump 2 and a Wesco pump 3 are provided on it. A suction port 5 and a discharge port 6 are provided on the centrifugal pump 2 and, equally, a suction port and a discharge port are independently provided on the Wesco pump 3. By controlling the velocity, and switching over the rotating direction, of the motor 1, a desired characteristic can be obtained from both pumps 2, 3, enabling the optional switchover of a water pressure and a water quantity.