Hi. I have a gas fired 333 F and I emptied the sytem to remove/flush all the radiators. I re-filled the water tank using the coding 02F:2. The pressure gauge did increase a bit but only to 1 bar. After firing up the system, it eventually increased to 2 bar. After a couple of weeks suddenly went down to 1 bar again. Tried venting, refilling until vent on back spurting water out. Cant get above 1 bar pressure. Any advice would be appreciated.