Abstract: A valve assembly is disclosed for an oscillating pump of the type having a reciprocating armature carrying an impeller that defines a pump chamber for flow of fluid through the pump. The valve assembly includes a valve body mounted to the impeller, a valve seat attached to the valve body, a spring retainer, a spring mounted to the spring retainer and a plug located between the spring and the valve seat. The valve assembly provides a substantially fluid tight seal when the pump is discharging fluid and allows fluid to enter the pump chamber when the pump is suctioning. All wetted components are particularly suitable for corrosive fluids, such as acids.