Leaking Radiator Bleed Valve

16 Feb 2009
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United Kingdom
We’ve noticed a very slight leak coming from the bleed valve in one of our upstairs radiators.

It only leaks when the heating is off which makes sense as it obviously expands when it’s warm and seals the leak.

The leak appears to be coming from the bottom of the hexagonal nut where it goes in to the radiator.

The rad has a thermo type valve at the bottom near the floor at the bleed valve side.

I would be grateful for any tips on how to go about fixing this.

Thanks in advance


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It probably leaks whenll it's on as well, but the drips evaporate before they are visible.
Is it leaking from the bleed hole or around the threads? Sounds like you suspect the threads.
Turn off both rad valves, open the bleed to release whatever little water is at the top of the rad, unscrew the whole bleed point with a spanner, (get a replacement if necessary) then screw the old or new one back in place with a few wraps of PTFE tape on the threads.
Then radiator on, bleed as normal, and happy life
Yes I recon the leak is coming from the threads.

I’ll get some ptfe tape and give that a go.

Is it necessary to count the number of turns made when turning the valve off?

Thanks very much for the advice. Much appreciated.
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O rings are alright and often on new rads, but PTFE would be more reliable if you can get enough turns on the amount of threads there are. Maybe the aren't sufficient threads on the bleed valve, but use your judgement!

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