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Thermostatic Valve Leak (Read 416 times)
Custard
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Thermostatic Valve Leak
Jun 3rd, 2020, 3:41pm
 
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!

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thescruff
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Re: Thermostatic Valve Leak
Reply #1 - Jun 3rd, 2020, 9:26pm
 
Hi,

No, turning off the lockshield valve is unlikely to keep you dry, as you'll need to drain the boiler/system and I would suggest replacing the valve if it's leaking around the pin.
I strongly suggest you buy yourself to a small tin of jointing compound and smear a small bit around the olives before you put it back and do the nuts up.
What are the boiler make/model and rough age?
Do you know how to refill the system and top the pressure up before you start?
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« Last Edit: Jun 3rd, 2020, 9:26pm by thescruff »  
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Re: Thermostatic Valve Leak
Reply #2 - Jun 4th, 2020, 2:28pm
 
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?
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Re: Thermostatic Valve Leak
Reply #3 - Jun 4th, 2020, 8:35pm
 
The pin will have an o-ring washer that seals it so not sure what the white part does, (Is there a make model on the valve) jointing compound would not work, it's used for sealing the connection with Olives, etc, instead of fitting them dry and then having leaks, which 9/10 plumbers tend to get. To drain it down you'll need to isolate the boiler 1st and the last pipe for heating then drain the radiators using a hosepipe on the draincocks assuming you have them at low points.
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Re: Thermostatic Valve Leak
Reply #4 - Jun 5th, 2020, 1:36pm
 
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

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Re: Thermostatic Valve Leak
Reply #5 - Jun 6th, 2020, 12:15am
 
The only way you could possibly stop that is to loosen the nut a couple of turns and wind a couple of wraps of Loctite 55 string under the nut and tighten it back up

Don't overdo it and remember the system is live so all sorts of things could go wrong.

Get the small loctite 55 string and store it in a cool place for future use.

The best plan is still to drain it out.
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Re: Thermostatic Valve Leak
Reply #6 - Jun 6th, 2020, 3:11pm
 
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?


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Re: Thermostatic Valve Leak
Reply #7 - Jun 6th, 2020, 8:45pm
 
It looks like you have 2 O rings seals 1 on the shaft and 1 in the white cap.

Get the small loctite 55 string and follow the instructions on the thread of the white cap, do not put too much one 3-4 turns should be plenty.

You can buy it at most builders and diy outlets.

https://www.bearing-king.co.uk/bearing/loctite-55-pipe-sealing-cord-50m/9058?gcl...
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« Last Edit: Jun 6th, 2020, 8:47pm by thescruff »  
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Re: Thermostatic Valve Leak
Reply #8 - Jun 7th, 2020, 10:19am
 
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?
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Re: Thermostatic Valve Leak
Reply #9 - Jun 7th, 2020, 7:10pm
 
A good chance the string will do the job, as I said don't overdo it though.

If you wanted to try it first wind it around about 4 times under the O ring, and see what it does.
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Re: Thermostatic Valve Leak
Reply #10 - Jun 7th, 2020, 10:38pm
 
OK - will do - thanks again!
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