Biasi boiler fault ERR 04 with low pressure

Hi tammy you should have 2 isolation valves with a silver or grey flexible hose connecting the 2. This should be located close to the boiler either directly underneath or behind washing machine or dishwasher if they are located underneath the boiler. The isolation valves should have handles on that you turn to repressurise or a slotted one which you will need a screwdriver for. If you cant find this your boiler may well have a internal filling loop. Hope this helps

I agree with JB heating. Please find your instruction manual if you have. Read it through there should be filling loop location if it built-in or manufacture provided. if not follow as Jb instruction.