Reciprocating Pumps are pumps which cause fluid to move by using one or more oscillating pistons, plungers or membranes. They require a system of suction and discharge valves to make sure the fluid moves in a positive direction. Pumps in this category can range from having one cylinder, up to four cylinders or more. They can be powered by air, electricity, belt driven from an external motor or even steam powered. Reciprocating pumps are used widely for pumping highly viscous fluids including concrete and heavy liquids such as oils. They are positive displacement pumps which have an expanding chamber on the suction side and a contracting chamber on the discharge side. The liquid flows into the pumps as the chamber on the suction side expands and the liquid then flows out of the discharge side as the chamber collapses. The volume is constant given each cycle of operation.