Common lift pump. In the upstroke of piston or bucket the lower valve opens and the valve in piston shuts ; air is exhausted' out of suction-pipe, and water rushes up to fill the vacuum. In down-stroke, lower valve is shut and valve in piston opens, and the water simply passes through the piston. The water above piston is lifted up; arid runs over out of spout at each up-stroke. This jump cannot raise water over thirty feet high.