Advice on radiator

[satnav10000]

One of my radiators although working correctly has for a very long time had a green powder forming at the top.
I am attaching photo hopefully! so you can advice please.

 

[ReganAndCarter]

Looks like you may have a slight weep around the air vent plug where it screws into rad. The calcium and other impurities in the ch system water are deposited as the water evaporates on the hot rad.

Try cleaning it up (cloth soaked in vinegar) and tightening the chrome plug with a spanner. If no joy, best to replace the vent plug.

https://www.plumbingworld.co.uk/chrome-1-2-radiator-air-vent-bleed-plug-7091

http://www.ebay.co.uk/itm/1-2-RADIA...322552?hash=item4af31cac78:g:AZkAAOSw5VFWMnXK

 

[John D v2.0]

Just a small leak evaporating as soon as it forms.
Try checking the bleed point is tightened, also the whole bleed nut might be loose as that sometimes happens when the bleed valve is opened.

If not, get a replacement o ring for the valve and fit it (with both radiator valves turned off.)

 

[satnav10000]

Just a small leak evaporating as soon as it forms.
Try checking the bleed point is tightened, also the whole bleed nut might be loose as that sometimes happens when the bleed valve is opened.

If not, get a replacement o ring for the valve and fit it (with both radiator valves turned off.)

Thanks for info, I assume if I replace O ring or vent plug with both valves off water escape should be minimal with no loss of system pressure.

 

[John D v2.0]

Thanks for info, I assume if I replace O ring or vent plug with both valves off water escape should be minimal with no loss of system pressure.

Yes, the top inch of water will come out and it'll be dirty water so prepare with old towels.
You'll need to open the valves again afterwards and bleed, then possibly a small top up.