Abstract: A double-acting diaphragm pump system for pumping and spraying materials, particularly corrosive liquids and abrasive fluids. The system includes a hydraulically driven double-acting diaphragm pmup which is electrically controlled for alternately pumping material through the dual pump chambers to an outlet pipe. The diaphragms of the double-acting pump are moved back and forth by a dual-acting hydraulic cylinder powered by a hydrostatic transmission for providing automatic response to pumped fluid needs, coupled with overpressure protection. An expansion tank maintains a constant pressure on the fluid as it is discharged from the pump. The system is capable of spraying abrasive slurries of a wide variety, at an even spray pattern, as the system wears, and hardened wear rings around the inlet and outlet valves permit the pump to be inexpensively rebuilt after extended use pumping abrasive slurries.