A method and apparatus of circulating cavitation fluid within a cavitation fluid circulatory system, before or during cavitation chamber operation, as well as a means of draining and filling the chamber with minimal, if any, exposure of the cavitation fluid to the outside environment, is provided. The apparatus includes a network of conduits coupling the cavitation chamber to a cavitation fluid reservoir and at least one external fluid pump. Preferably the cavitation fluid reservoir serves the dual function of dual reservoir and degassing chamber. Manipulation of various valves within the conduit network allows the cavitation fluid to either be pumped from the reservoir into the cavitation chamber of from the cavitation chamber into the reservoir. A vacuum pump coupled to the degassing system can operate continuously or intermittently. The cavitation fluid circulation system can include a bubble trap and/or a heat exchange system.