A double displacement pump includes an inlet manifold, an outlet manifold, a first fluid cavity between the inlet manifold and the outlet manifold, a second fluid cavity between the inlet manifold and the outlet manifold, and a drive system that includes a housing defining an internal pressure chamber, a piston disposed within the internal pressure chamber and having a first and second pull chambers and a central slot for receiving a drive, a first pull with a free end slidably secured within the first pull chamber and a second pull with a free end slidably secured within the second pull chamber, and a first fluid displacement member coupled to the first pull and a second fluid displacement member coupled to the second pull.