Hello – I have a small leak in my thermostatic radiator valve. I have cautiously tightened the two nuts shown in the image where the leak is coming from (i.e. the white one and the brass one with the green oxide coating) by about a quarter turn. It still leaks. What would you advise?

Would closing off the lockshield valve at the other end temporarily halt the leak whilst I repair it?

My heating system is a combi boiler.

Many thanks in advance people!

Thanks Thescruff – it's kind of you to take the trouble to reply.

I don't know how to drain the system (I do know how to re-pressurise the boiler for what that's worth). The boiler is an Ideal Independent C24 – probably 6 or 7 years old at a guess as it came with the flat.

I slackened off the white nut that's part of the pin valve and then re-tightened it and it leaks less now. Maybe a bead of water every hour or so now. Hard to tell if it's the pin or the nut that's letting the water out. Before I saw your post, I closed the lockshield as I figured it would do no harm (I hope).

Can you replace just the 'pin' element of the valve to fix such a leak?

*Quick update:* I've been monitoring it all day and I'm pretty sure the water is coming from between the white plastic 'pin' component and the brass nut – as the 'pin' itself always seems to be dry. If I cleaned the two opposing surfaces and applied jointing compound maybe?

Apologies, I might not have been clear. The water is coming from between the white plastic item and the brass hex nut. On the image I have indicated a VERY tiny droplet (you may have to click on it to make it larger to see) that forms on the ledge of the protruding triangular bit of the hex nut.

I unscrewed the white bit, cleaned up the rubber grommet inside and the top of the brass hex nut but wonder if a bit of something applied between the two surfaces might help (silicon? jointing compound - no?). There is no branding or make on the valve I'm afraid.

Thank you again

Thank you for the reply. I'm not too sure I feel confident to drain down the system. I think that might be better left to the pros when they let them out of lock-down. So the Locktight thread string might be a temporary solution until then - thanks for the tip.

I did completely remove the plastic nut as you can see balanced to the left on the pipe in the image below. I don't quite get the mechanism but absolutely no water comes out when it's like this. I guess the valve is shut when it's like this?

Thanks Thescruff for your advice. I had already ordered the Locktight string from your previous post (coincidentally from Bearing King too!)

Since it's such a tiny leak, do you think the string will hold OK or is it crucial to go to the expense of getting a pro to drain down system/replace the TRV etc?

OK - will do - thanks again!