A regulated automatic changeover valve is provided. A device engages the first and second high pressure gas source for providing a lower pressure gas source downstream of the changeover valve. An eccentric is provided between two valve assemblies, with each valve assembly having a piston with a valve arm projecting therefrom. The eccentric moves a block selectively closer to one of the two valve assemblies. Each valve assembly is engaged to a high pressure source, such as a tank of compressed gas. When a first tank begins to run low, the valve will automatically begin drawing from the second valve assembly. A tank that has run low of compressed gas may be changed out while the second, non-exhausted gas continues to feed the downstream device at a regulated gas pressure.