Inhibitor in sealed c/h system..?

Evening all -

Apologies if this is a daft question - but how am I supposed to introduce a corrosion inhibitor into a sealed (ie pressurised) central heating system...? Clearly in a vented system I'd add it to the header tank... but.... ? Is there usually some point on the boiler at which I can add it...? Don't much fancy squirting it through the bleed valve of a radiator ! My Mum has an 8mm microbore system and I need to change a leaky valve for her... and as I understand it an inhibitor is pretty much essential in such narrow pipework.

Thanks in advance. Kind Regards - Chris.

drain down some to allow some water out (one you have tested the system for leaks if u are working on it !)....undo the bleed valve (the whole nut) and use an elbow compression and a funnel. (undo other side to allow air out)
(if you have a towel rail use that one as has valves on top of rad !)

Multiple ways to do it, all of varying hassle. All pretty much require that it's depressurised at the very least: but it you're changing a valve that won't be a problem:-

1. Use of caulk gun style pack of inhibitor to squirt it into a radiator.

2. If you have a towel rail that has the caps on the top, take a cap off and pour it in (let some water out of system first though!).

3. take off a radiator (with the valves still on the radiator - undo the pipe unions). turn radiator upside down. open valves, pour inhibitor in. turn valves off. refit rad. refill system, when you're sure there are no leaks, open the rad valves to let inhibitor in.

I don't recommend using the radiator on which you are changing the valve on for the inhibitor if you go with method 3. You may only find out that your valve leaks after you let the inhibitor into the system - and you thus lose the advantage that the inhibitor is locked inside one rad until you know there are no leaks.

Cheers

slip

Fernox sell a kit to do this fairly easily at a radiator vent. You can find it at places like Homebase

Nice one - thanks all for replies.

Sounds like I do in fact need to get the stuff into the system via a rad - I thought this through before asking the question, and it was the only way I could see too, but I suppose it just seemed so unlikely that I couldn't believe it was the only way. But your advice has confirmed it.

Thanks to all. Kind Regards.