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I have an oil fired Worcester combi boiler which is pretty old now - around 20 years old in fact. I know it needs replaced but was hoping to get one more winter out of it. Over the past few days it has been losing pressure very quickly, dropping to almost '0' overnight when it is off and this is far quicker than I have experienced with it before. However I have noticed something strange. If I do not bother topping up with the filling loop, when the timer kicks in and the boiler fires up again, it regains its working pressure again all by itself within 20-30 minutes and it retains it while it is working. I have never come across this before. Can anyone shed any light on what is happening before i call out my local engineer?

Hi shalebing,
Such dramatic loss of pressure probably indicates that you have a leak on the primary system and that the pressure vessel has failed. When the boiler fires up air in the system will expand restoring some pressure in the system.
Regards S