- There were several problems in the FDC parts of the gas system. A series of graphs (from Mike) linked above demonstrate some of them. A 1 l/min leak was found due to bad fitting of one of the valves and later fixed: first graph shows the pressure in the mixing tank (red is FDC) with ~2 l/min filling flow and 0.4l/m FDC usage. To identify the place we were excluding different parts of the system. Once the tank was insulated (flat part in second graph) there was still some pressure drop; it turned out there's a small leak from the relief valve on top of the FDC mixing tank. Same valve is used on the CDC tank but it has not been checked.