By intergrating a one-piece pump body, sealing portions re reduced in number to prevent liquids from entering due to sealing defects. A rubber gasket is provided between the pump head and the bracket to prevent water from entering through the periphery of the pump head. To keep the controller unit watertight, a plastic cover with gasket is provided as standard equipment. The adoption of membrane switches for the controller panel is another measure for the prevention of liquid penetration.