It is a combi boiler, and it's happened every year for 4 years, and yes, Expansion Vessel does ring a bell, but as far as I know they just kept pumping it up. Obviously I know now that adding water regularly like this can cause problems, but I'm not a plumbing engineer and I didn't know before this last set of problems - surely it was up to the BG engineers to tell me it needed inhibitors or whatever, or deal with this problem during the last 4 years before it became a big problem? Sludge and aggressive water don't mean anything to a non-technical person, not that they were even mentioned until my boiler stopped working completely recently. BG say their power flush will cost more than anyone elses because it comes with a lifetime guarantee (although apparently there is no paperwork provided to show this), is this guarantee worth paying extra for, does anyone know?

BG tring to get me to have a powerflush (including magnaclean) at £695, reduced to £468 after they've made too many cockups to mention which meant I had no heating or hot water for 2 weeks. Not sure if I'm benefitting from £227 compensation or being conned, but either way I'm expected to cough up nearly £500 when the sole reason for paying for HomeCover was to prevent unexpected large bills. How can I tell if I need the powerflush or not? The central heating system is 10 years old, but they've replaced virtually every part in the boiler now, including pump, main heat exchanger and secondary heat exchanger. Some of the radiators have cold bits near the bottom. He showed me some tiny black bits in some of the parts he removed which he said was sludge. For the last 4 years, the boiler has been fine for months, then gradually started losing water pressure so I have to top it up manually, when it got to every couple of days I'd call them out, they'd solve it (by pumping air in??) then the process would start again. Should BG have identified this sludge problem earlier from that? They never added any inhibitor even though I was toppping up the water regularly, has this led to the problems I've got now?