What other ways for getting inhibitor into closed CH system ?

[andysideas]

I have read the FAQ CH guide.

However this seems like a rough science.

If I understand correctly I should totally drain the system first, then get the inhibitor in before filling ?

Alternatively I have seen this

Any thoughts

[Sponix]

What I do is drain off some water via the drain tap. Then, I remove a big metal plug from one of my rads* and pour the inhibitor in using some rubber pipe and a funnel. Re-fit the plug, re-pressurise then bleed.

(*Not all rads have big metal plugs)

sponix

[Andy Hall]

No you don't need to do that provided that the system is clean and has been kept up to date with inhibitor.

If the system is open vented, then the standard way is to add a good quality inhibitor like Fernox MB-1 to the header tank after having drained some water off. There's no point in alternatives.

For sealed systems, you can isolate a radiator, empty it and siphon liquid inhibitor in through a vent. Another option is to plumb in a short vertical pipe somewhere with isolating valve and siphon inhibitor into that. This method needs the system to be depressurised and part drained.

Another approach is to use gel inhibitor like Fernox Super. This is injected using a mastic gun into a radiator vent. However, I don't go by the recommendation of doing so against system pressure because typically the little nozzle doesn't seal well. So again the technique is to isolate and part drain a radiator. This is the method I currently use.

For a secondary circuit, I have an antifreeze inhibitor that I need to save when the system is maintained because it is expensive. For that I devised a way of putting it back into the system using a compressed air plant sprayer and adaptor to the filling loop. Cost about £12 for the sprayer plus bits. THis could equally well be used for injecting MB-1 into the main system if I wanted.

THe Rapid dose thing looks interesting and is basically the same concept. As far as radiators are concerned, use may not be possible because many slim panel ones don't have tappings with plugs at the top. Nevertheless, the filling loop option is viable.

However, my question mark would be "Who is Aqueous Logic?" Their products may be OK in terms of the efficacy of the inhibitor - I don't know. I do know that I've used Fernox stuff for 30 years and it works properly and predictably. It costs more than other products, but since the system replacement cost for a heating system is several £k, the difference is insignificant. Although the Rapid Dose idea is a nice concept and convenient to use, I don't see a reason (for me at least) to change to using it.