The anti-corrosion inhibitor (Sentinel X100) in my open-vented CH system has become diluted and losing its effectiveness, so needs to be topped-up. I am /assuming/ that simply pouring more into the header tank probably won't get it into the bulk of the circulating water - is that correct? Apart from draining down part of the system (thereby losing some of what is there already :-( ), adding the extra, then re-filling, any other suggestions please???

Chris, December 2007

Since the existing inhibitor will be well mixed, you will add much more inhibitor than you loose if you very slightly drain the system. (Best to empty the header tank first, to make sure what you add all goes into the system).

Mark, December 2007