A valve arrangement is provided that more effectively purges processing liquid from a processing liquid delivery system. With the valve arrangement only a small portion of the processing liquid path having a small wetting perimeter must be purged to affect replacement of a dysfunctional injection valve or any other component within the processing liquid delivery system. The valve arrangement comprises a first and a second isolation valve, a pump valve and purge valve configured to reduce the wetting perimeter defined by the four valves. The valve arrangement allows a dysfunctional injection valve or any other component to be replaced without health risk to humans or damage risk to a processing liquid delivery system employing the valve arrangement. During component replacement, the first and the second isolation valves are closed and the pump and the purge valves are opened so as to purge processing liquid from the isolated volume defined by the four valves. Pump/purge cycles preferably are performed, and the purging process may be performed automatically or manufally. Once the isolated volume is purged, one of the isolation valves and the component are removed and replaced as a unit.