I'm currently flushing out my CH system (as I write, trying to dislodge
airlocks...! :-( ) and hopefully will be in a position to add some new
inhibitor.

I'm wondering how much I need to add, in that I haven't a clue what the
internal volume of my (sealed) system is. I have 15 rads/towel rails of
varying sizes (with mixture of 22/15/10 mm pipework if that makes any
difference) .

Any ideas as to a ballpark figure? As I'm adding Sentinel X100, which
needs 1 bottle per 100 litres, I'm asking should I be adding one bottle
or three?

Thanks
David