"Christian McArdle" wrote:

Now Ive remembered Im trying to figure out where to add it. The only
possibles are the filling valve or a radiator bleed valve as far as I can
see.

It depends if you don't mind doing a bit of plumbing.

You're supposed to use a messy injector syringe which sprays the inhibitor
all over the room.

Or if you have a towel rail then close all the other radiator valves
except the towel rail, part drain the system (if you drain to a bucket
you can see how much has come out) take off the bleed valve/blanking
plug, pour in the inhibitor, tighten everything up, refill and
rebleed, check the pressure again and adjust as necessary.
Start to finish it could take less than an hour. Of course without a
towel rail you are knackered.
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