The piston pump can be defined as it is a positive displacement pump. These pumps use a piston, diaphragm, otherwise plunger for moving liquids. These pumps use check valves as the input and output valves. The general piston-pump is a rotary pump which uses a wheel or revolving shaft for operating the piston. The revolving component can be connected to a shaft from its center http://www.oilmaxhydraulic.com/piston-pumps/