A well pump system that comprises: a pressure pipe; a rotatable shaft surrounded by a plurality of bearings; a pumping mechanism mounted to the pressure pipe and having a plurality of pump impellers mounted to a second end of the shaft; a rotating mechanism mounted to a first end of the shaft and configured for rotating it within the bearings, thereby causing the pump impellers to move the fluid in the pressure pipe; and at least one non-return valve configured for assuming at least two states: a first, opened state, in which the second pipe chamber is in fluid communication with the first pipe chamber, and a second, closed state, in which the non-return valve obstructs the fluid communication between the first and the second pipe chambers, thereby lubricating them.