Which inhibitor and what quantity to add?

[nelectric]

Recently replaced a diverter/zone valve and that involved draining practically all the water in the CH system. Realise now, after refilling, that inhibitor ought to be added. System is vented but the F&E tank is VERY difficult to get at, so will have to add to a radiator.

Have read that Fernox is better than Sentinel for this type of system as Fernox contains antibacterial growth protection - is this correct?

I see there is Fernox MB-1 and Fernox Alphi-11 - which should I use? And how much of it? They come in 4 litre and 5 litres containers respectively. Do you add it all, or do you calculate size of system (number and size of rads, number of floors etc) and just add an appropriate amount?

Is it easy to add via a radiator? Should I buy some sort of funnel or filling kit?

Lots of questions - you may have guessed it, but I haven't done this before

 

[glasgowgas]

sentinel x100 and bung in the full litre, job done

 

[Happyplumber]

I agree i normally use FX 100 ,if you need the anti freeze then use the alphi ,either of them are excellent products one bottle normally does an average three bedroom house with ten rads