A hand pump for pumping out fluid from a reservoir, comprising a pump body, a faucet, a driving mechanism and a sealing arrangement. The pump body has at a side a connector defining a receptacle radially extending into a cavity of the pump body. The driving mechanism includes an axle inserted in the receptacle of the connector, a sealing sleeve mounted around the axle, a coupling cap axially secured to the sealing sleeve, and a L-shaped handle. The handle having at one end inserted through the coupling cap and the axle, and at the other hand extending outside the coupling cap. Operation of the handle in cyclically up and down motion drives the axle to rotate, which causes a piston in the cavity to move upward and downward so as to suck the fluid into the faucet. The sealing arrangement has at least three O-rings disposed among the parts of the driving mechanism to provide an effective seal between the driving mechanism and the pump body.