Leaking compression joint

[trialsrider]

Well I was disappointed to see a leak coming from the compression fitting on my water heater. It is a newly installed webasto isotemp slim 20.

 

I have recently installed hot water in my van and only finished the install a few weeks ago.

 

The leak is coming from the Joint which connects the hot output to the thermostatic mixer valve. It's ironic as it is one of the few joints I didn't do myself as it came fitted in the box. I must confess I did rotate the fitting a bit so that the mixer valve was at a better angle to access and this may attribute to the leak.

 

I've tried nipping up the compression joint by tightening it. This usually remedies any leak in my house but it still leaks.

 

I'm convinced it is the seal around the olive that is failing as the thread itself is just for tension. I used loctite 577 on all the brass threaded hose fittings you can see in the picture but I think it is only suitable for threads so wouldn't help here.

 

I'm considering wrapping the olive in a few wraps of PTFE tape but that seems a bit of a botch job. Or is this satisfactory ? Any recommendations to remedy this leak? Or is olive removal the only solution and start again ?

 

[weldted]

Toolstation sell a silicone that is especially for this type of joint,

[Ninian]

Hi, I would wrap the joint in PTFE. If you saw off the olive an indent will already be present and trying to fit another olive possibly a few mm from it you could end up making the leak far worse. For me PTFE the way to go.

[davidmac]

Hi I would suggest going to your local plumbing supply shop and getting a tub of "boss white". Take the joint apart, smear a small amount around the olive and re assemble. Its old school but has always worked for my plumbing jobs.

Regards David

If the joint has been tightened properly the olive will have squeezed into the pipe and you will not be able to remove it. The olive should be between 6 and10 mm from the end of the pipe .

[trialsrider]

davidmac - 2020-11-20 7:29 PM

 

Hi I would suggest going to your local plumbing supply shop and getting a tub of "boss white". Take the joint apart, smear a small amount around the olive and re assemble. Its old school but has always worked for my plumbing jobs.

Regards David

If the joint has been tightened properly the olive will have squeezed into the pipe and you will not be able to remove it. The olive should be between 6 and10 mm from the end of the pipe .

 

They sell that in b&q so that could be an option. The. Pipe is about 2mm thick stainless steel not copper so I reckon an olive puller would get it off. I would rather not attempt removing it though.

[trialsrider]

Ninian - 2020-11-20 7:15 PM

 

Hi, I would wrap the joint in PTFE. If you saw off the olive an indent will already be present and trying to fit another olive possibly a few mm from it you could end up making the leak far worse. For me PTFE the way to go.

 

I was thinking the same. Is PTFE going to be ok with the high temperature of the hot output ?

[colin]

Fernox LS-X is what you need.

[trialsrider]

colin - 2020-11-20 8:32 PM

 

Fernox LS-X is what you need.

 

I see they sell that in b&q too. Have you used it ?

[colin]

Always have a tube of it in the toolbox. A smear around the olive should do the job.

[Mickt]

They also PTFE in a tube, this should work ok

[Derek Uzzell]

These couple of links may be useful

 

https://www.familyhandyman.com/project/stop-leaks-in-plumbing-joints/

 

https://www.pvcfittingsonline.com/resource-center/pipe-thread-sealant-vs-pipe-joint-compound/

 

A compression fitting should not leak when tightened up if all its compaonents are in good condition and properly aligned.

 

PTFE tape is not intended for sealing a leak at the olive, but a pipe-joint compound like Fernox “Water Hawk” should be effective.

 

https://fernox.com/product/water-hawk/

 

 

I use Fernox LS-X

 

https://fernox.com/product/ls-x-external-leak-sealer-50ml/

 

liberally when DIY plumbing, but a badly leaking compression joint may need somehing more radical.

 

(Before resorting to tape or any sort of jointing compound, I’d try lubricating the fitting’s female thread and the olive with a PTFE spray and then tightening up the joint really hard. As the pipe is stainless steel, it should be able to tolerate reasonably brutal treatment.)

[Alanb]

trialsrider - 2020-11-20 7:59 PM

 

Ninian - 2020-11-20 7:15 PM

 

Hi, I would wrap the joint in PTFE. If you saw off the olive an indent will already be present and trying to fit another olive possibly a few mm from it you could end up making the leak far worse. For me PTFE the way to go.

 

I was thinking the same. Is PTFE going to be ok with the high temperature of the hot output ?

I am not aware of any problem with PTFE tape, at such relatively low temperatures.

 

If you choose to use PTFE tape, there should not be any problems, if in the future you should need to replace the thermostatic valve. I am not so sure about other sealants,some of which tend to set like glue.

 

Alan

[laimeduck]

Hi

I can recommend this stuff - Fernox LS-X Leak Sealer. About £5 from Screwfix and widely available.

https://tinyurl.com/y2g9r9m3

 

I was recommended by a very trustworthy brown coat old style builders merchants it in the 1990's when I re-furbished my bathroom and used it on all compression joints for hot water and radiators, and now always use it on compression fittings.

I have never had a leak after using it.

 

And I HATE plumbing!

Worth a try?

 

Jeremy

 

[Mickt]

I always use PTFE on house radiator valves , they get hot

[trialsrider]

Thanks for all your responses . Very helpful as usual. Like most of you I guess, I already have PTFE tape at my disposal. So I tried it this morning both over the olive and thread and so far after an hour no leak to report under pressure. I've now switched on the heater so I can test the joints when they are hot. Fingers crossed !! If it does leak I'll go down the jointing paste route many of you have suggested. Thanks once again.