leaking rad tail

18 Aug 2005
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United Kingdom
hi guys,

i put up a new rad today, and i'm finding the tail for the TRV is leaking at the joint at the rad. I've done and undone the tail about 4 times and tried extra ptfe, and boss green jointing compound (separately), but i still can't stop the leak - it's about 1 drip every minute, so i'm not sure what to do. I've done a search and folk have mentioned using LSX or loctite string - what would you recommend to use in this situation?

cheers guys
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You have not mentioned the make of rad or TRV.

Many seem to be cut too deeply!

I always teach trainees to wrap 10 turns of PTFE in the correct direction on the tail and to do it up four finger tight!

No other jointing material is required.

Thats a decent TRV.

I only ever use gas ptfe on everything and never seem to have any problems.

Have a close look at the rad for a small crack or hole.
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I normally wind the tail without PTFE into the rad (especially on rads I'm not familiar with) so see how tight the fit is and to clean out the thread.

Then wind the PTFE in a taper shape. Always works for me.

Normally the only problem with the Danfoss TRV's is from the compresion fitting onto the tail. They overdo the chrome and the thread tends to be a little tight. A good smear of Hawk White on the olive and thread sorts it.
Could be your ptfe winding technique! If loose it can all push back when you wind the fitting in.
First, drag eg a hacksaw blade across the threads hard, so you scratch all the peaks.
Wind the tape on clockwise looking from the radiator end. A little less at the very end will help it go in.
Then run your thumbnail into the thread all the way up the thread.
Some rads need a lot of tape. Using the usual small tad valve tools, you should have to use a lot of strength with one of those when the fitting gets to the position you want

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