Advice On Adding Corrosion Inhibitor Please ??

15 Dec 2007
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United Kingdom
I have a combi with 10mm microbore heating circuit. I drained the system, renewed two double radiators (from Screwfix) and re-filled the system with plain water via loop. Everything working fine.

I then needed to add inhibitor. I closed the valves on one of the new rads, and drained the water from it. I then removed the chrome blanking plug at the top corner of the rad, and tried to pour in inhibitor via a funnel and piece of tube. As fast as I was pouring the inhibitor in, it was running back out the blanking plug hole.

I now realise that this is not the way to do it. What are my options for adding inhibitor? I would prefer to add it to a radiator, rather than having to drain the whole system. Should I add the the concentrated type through the air vent. What's the method for this? Any other options?

Please help before my system rusts too much!!
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Simplest way is do what you have done then get a compression elbow take nut off and screw it into hole and it will pour in now (slowly)
Thats how I do it as well namsag. take the blanking plug out though, then you can fill from that end whilst having the air bleed open the other. This should stop it 'glugging' out due to air locks in the rad.
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if you open the drain cock again, then the bleed valve on that one radiator, you will drop the water level enough to be able to use your funnel method. you will need a bit of tube poked through the hole as well.

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