Hi all just wanted to post some info about my recent worcester 30si problem it was losing pressure when heating off but gaining pressure when on up to 3.5 bar down to 0.5 when off vessel checked all ok everyone was saying leak in system all were ok when worcester engineer called as its under warranty it was a blocked pipe from central heating rads to boiler when he removed pipe and unblocked it expelled a load of sludge now working fine tip top happy lady again I would like to add my system is only 2 year old and now I intend to get it flushed again to stop this issue in the future hope this helps anyone encountering the same issue because after regading some posts on here i was having nightmares of ripping up floors etc to look for a leak