Embodiments of the invention generally provide an etchant mixing assembly for a semiconductor processing system. The etchant mixing assembly includes at least one acid source, at least one oxidizer source, a mixing tank selectively in fluid communication with the at least one acid source and the at least one oxidizer source, and a mixed etchant tank in fluid communication with the mixing tank. Additionally, a system controller configured to sense a low level of fluid in the mixed etchant tank, cause a fresh fluid solution to be mixed in the mixing tank, and cause the fresh fluid solution to the communicated to the mixed etchant tank is also provided in the etchant mixing assembly.