Thanks, just on that topic for future what should good practice be with adding additional inhibitor? Presumably the odd re-pressurisation is OK but if you replace a radiator or whatever you need to add more water back. Is there a rule of thumb here when and how much inhibitor to add?
The actual amount in the system is not that critical. Some suggest that you always top up, with the same inhibitor as is already in there. Best way is read the instruction on the bottle of inhibitor, the number of radiators it is enough for, then from that calculate the amount you need to add.
I your system was up to spec with inhibitor before the radiator was replaced, then it will be fine without needing to add any. However, a couple of years ago, I half drained my system, to swap a valve out. So when refilling, I took the precaution of adding half a bottle of inhibitor.
We were advised to have it done as the system was filthy and causing damage. But how can one tell if the cleanse was not done well, or something else is to blame... what sort of things can be missed when doing a flush? I am imagining things like missing a radiator perhaps - everything looks good but then than radiator dumps a load of rubbish back in?
I think the point is to just make sure the flushing is done to ensure it is done in a logical way, such that the dirt and debris it flushed out, rather than simply being flushed to another part of the system. Impractical, but ideally - every radiator needs to be removed and individually flushed through outside, then every individual pipe flushed separately.
My own system is 40 years old and always maintained by - me. It has always had inhibitor in it, never actually needed any flushing, always spotlessly clean inside. New boiler fitted a couple of years ago, so I decided to give it its first ever flush through, whilst watching what came out. Nothing at all was flushed out of it, except perfectly clear water, plus inhibitor.
A magnetic filter was advised by the boiler manufacturer, I fitted one and I have checked it several times since then, but it has collected almost nothing.
Obviously, the problem is that most systems are not maintained, not looked after at all. People only become concerned, when they stop working. The assume an annual boiler check or service, checks their whole system out. No one ever worries about the inhibitor, so the system slowly rusts away from the inside. It applies equally to big commercial systems as it does to small domestic systems - both get neglected.