It was a twin suction force piston pump for fluids, invented by Ktesibios in the 3rd century B.C. and continues to be in extensive use in various forms until today.
It consisted of two pistons that reciprocated with the help of pivoted levers and handles within two vertical cylindrical containers immersed in the water source. In the raised bottom of the containers there were non-return valves for the incoming water. The outlet pipes led to the bottom of the middle container that had the non-return valves for the discharge water. At the ascendant movement of the piston, vacuum and suction of the water were produced. At the descendant movement of the piston the water was forced into the middle container that had an airtight hood like an inverted funnel and a directional discharge pipe. The alternating opposite movement of the pistons caused the continuous flow of water with force.