Leaking radiator joints

[Mike Clarke]

I've replaced some radiator valves with TRVs and I've got a problem with water seeping out of the joint between the valve and the tail on one radiator. I've tried tightening up the joint to the point where it doesn't seem to want to go any further and I'm a bit reluctant to apply any more force in case I strip the thread.

The original valves and the TRVs both had tails with 1/2 inch compression fittings so I thought I'd keep things simple by reusing the existing tails and avoid the possibility of introducing leaks round the threads of the tails if I replaced them. Perhaps this was a bad move and I was tempting fate by re-using the old olives already stuck on the tails.

My choices now seem to be:

1) Try to tighten even further at the risk of overdoing something.

2) Strip it down again and replace the tail. If I do this then how much PTFE tape do I need to use and how tight does the tail have to be screwed in?

3) Strip down, leave the tail in place, carefully remove the old olive with a junior hacksaw and use a new olive.

Any suggestions on the best approach?

[The Medway Handyman]

Try running a leak sealer through the system.

[david ryan]

What a cowboy! Try fitting the TRV properly using a new olive, don't use all the old crappy stuff. Don't forget your PTFE tape!

[John Rumm]

It sounds rather like he has replaced the whole valve but not the stub that screws into the rad (which is where you would need the PTFE).

Assuming this is the case, then replacing the olive may well fix your problem. One thing to note is the amount of pipe that slides into a compression fitting (and hence the position of the olive) is not standard. So you can find times where you are unable to get a seal with a new fitting and old olive simply because it is too far from the end of the pipe and this prevents it seating in the right place.

[The Medway Handyman]

Doh! PTFE tape on a fitting that seals via the olive not the thread?

[1501]

Assuming the length of the tail doesn't stop the olive seating I'd recommend just a smear of boss white on the olive if it is to be reused.

[Lurch]

On Thu, 16 Aug 2007 00:16:11 +0100, "The Medway Handyman" mused:

Where would you put the PTFE then? Not on the thread surely, as this would be insanity, as you pointed out.

[The Medway Handyman]

My mistake, I thought you were suggesting PTFE on the compression fitting thread.

[Mike Clarke]

Yes, I left the original tail in place with the existing olive. If I'd replaced the tail then it would have needed tape round the thread that fits into the radiator but as I understand it there's little point in putting PTFE tape on an olive and it might even be a bad thing.

Yes, that turned out to be the problem. I took the whole radiator off the wall for a closer look and the new valve was just not quite contacting the olive. Then I realised I couldn't use the hacksaw and screwdriver trick to remove the olive because access was restricted by the nut but a few hammer blows on a large spanner behind the nut pushed the olive off. Reassembly with the nut and olive that came with the TRV cured things. Thanks for the advice.

[John Rumm]

That's right. The only "improper" use of PTFE I find useful sometimes is on the thread of a some compression fittings purely to act as a lubricant.

The other solution that can sometimes work in this case is to just hacksaw the very end of the pipe off, shortening the distance between the end of the pipe and the olive. (obviously there needs to be enough give in the tail to enable it to pull into position, a little higher than before)

[The Medway Handyman]

Indeedy. Some can be a trifle 'sticky' to do up.

Glad its not just me :-)

[John Rumm]

And squeaky!

Saves you smelling like Boss White for three days after as well! (which also cause premature failure of latex gloves - which I tend to use if doing much plumbing to keep the grime off the mits)

[Andy Hall]

Wonderful stuff, Boss White. Everyone doing DIY plumbing should put a smear behind each ear to demonstrate that they are a Real Man (tm).

[Dave Plowman (News)]

A compression fitting shouldn't need excessive force.

This is the bit twixt valve and rad? Just run a couple of layers of PTFE round it and set it to the same distance as the old.

On all the 'tails' I've seen the olive is part of the tail - not separate as on a pipe. However not all tails have the same profile olive so I'd always use the new supplied one - unless simply replacing the same make valve.

Fernox LS-X is a truly excellent product for sealing leaks - but really shouldn't be needed on something as simple as this.