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Sealing compression fittings with Fernox LS-X


blackrose

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Ive decided to seal up all the compression fittings on my central heating system with Fernox LS-X.

 

It was never a problem in the past, but because I'm now using antifreeze rather than inhibitor the viscosity of the water is reduced and I want to eliminate the possibility of future leaks in the middle of winter.

 

So, would it be ok to take off the compression nuts and smear some LS-X over the the olives where they meet the fitting and then screw the nuts back up, or do I have to dismantle the entire system so that I can get sealant into the inner face of the olives?

 

Windsor20and20Maidenhead-20120914-00009-1.jpg

Edited by blackrose
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Mike, you are wasting your time - it won't leak

 

Richard

 

But it was leaking Richard. The old part of the system was fine but I really had to tighten the fittings where I'd modified the system to get it to stop. Even then there were one or two slight drips. I don't think the new olives are as good.

Edited by blackrose
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Mike, as an aircraft fuel systems apprentice, we used simple metal to metal seals to hold 5000psi of low-viscosity kerosene at over 100C

 

My prediction is that all you will do is squeeze the goo out and seal on the metal faces - like they are supposed to

 

In addition, you'll upset several joins that seal OK now and make them leak

 

Richard

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Keep disturbing them without renewing the olives is not good. I'd just go round them checking for tightness.

 

Mike, as an aircraft fuel systems apprentice, we used simple metal to metal seals to hold 5000psi of low-viscosity kerosene at over 100C

Richard

 

I bet they were better quality seals than the ones I'm using!

 

My prediction is that all you will do is squeeze the goo out and seal on the metal faces - like they are supposed to

 

In addition, you'll upset several joins that seal OK now and make them leak

 

Richard

 

Ok, I just called Fernox who said that LS-X needs to be in the inner face of the olive. Sod that for a lark. I'm not going to dismantle the entire system.

 

What about wrapping some PTFE tape around the part of the olive and thread that I can see?

Edited by blackrose
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I bet they were better quality seals than the ones I'm using!

 

 

 

Ok, I just called Fernox who said that LS-X needs to be in the inner face of the olive. Sod that for a lark. I'm not going to dismantle the entire system.

 

What about wrapping some PTFE tape around the part of the olive and thread that I can see?

I wouldn't, just place a bowl beneath each fitting just in case. And i wouldn't have the antifreeze mixture too strong, 2 parts water to 1 part antifreeze should be quite sufficient, and use rain, river, distilled or de-ionized water.

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Nuts and olives work very well as long as they are not overtightened and its a good thing to go back around them a week later with the spanners(ones that are near enough)and just check as heating up and cooling down in any degree can stretch them initially.

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This is certainly different advice to that given a week or so ago on another thread. Then most people were saying they always use PTFE, boss white or LS-X with compression fittings.

Twernt me. I said tape on tapered threads and boss white and hemp on parallel threads, nothing about sticking anything on olives.

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What about wrapping some PTFE tape around the part of the olive and thread that I can see?

I'd try it as described in the other thread. It won't provide a seal but lubricate between the olive/fitting and the compression nut, allowing more torque to tighten down on the olive.

 

Copper olives should seal fine unless overtightened or there's a deep scratch in the pipe or the inside of the fitting where the olive goes.

 

If all fails, I'd put some LSX on the olive, fitting thread, compression nut, should seal fine.

 

Edit It's not a bad idea to practice with 2" long pipe offcuts and spare olives to see how much force is needed.

 

cheers,

Pete.

Edited by smileypete
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So, would it be ok to take off the compression nuts and smear some LS-X over the the olives where they meet the fitting and then screw the nuts back up,

Yes.

 

 

or do I have to dismantle the entire system so that I can get sealant into the inner face of the olives?

No.

 

 

Hope that helps, :)

Mike

 

Nuts and olives work very well as long as they are not overtightened

 

Equally they must not be undertightened.

 

As I said in Mike's other thread on the same subject, they need to be tightened the correct number of turns, as stated in the fitting manufacturer's instructions.

 

 

Miie

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Just use plastic piping its easier!

 

Not from the back of a stove it isn't!

 

 

Well, I took off the new bit of copper plumbing and put it all back together with LS-X all over the olives. I didn't see Mike's post until afterwards, but Fernox told me the sealant would have to be on the face of the olive that goes into the fitting. Anyway, it seems to be fine now - I can't find any leaks and the water level is staying put against the mark I've made on the header tank. I'll check all the fittings again once it gets colder and I've lit the stove.

 

Fernox LSX was only invented to keep numpty plumbers from having leaks that why British Gas buys 80% of the shiite!!

 

never used it in over 30 years of heating/plumbing, boss white and jet blue very occassionally, gas seal & PTFE gas tape being my prefered things

 

Well, as a numpty plumber I can confirm LS-X works!

 

If you've never used it how do you know it's shite and why is using it any worse than using boss white or jet blue? They were probably invented for numpty plumbers too!

Edited by blackrose
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I've been through all the variations over many years as an amateur plumber and this is what I've ended up with and it works every time.

 

Only using pipe & fittings that are in a good state.

 

Use pipe cutters not a hacksaw.

 

Make sure the fittings meet the pipe squarely and that you are not trying to absorb 2 or 3 degrees of bend.

 

Clean the pipe where it goes in the joint AND the olive (this inside and out) with wire wool. (Horrid stuff.) until clean and uniformly bright. My justification for this is that it removes the thin layer of metal oxides and gives softer mating surfaces. Probably nonsense but it works.

 

Wrap PTFE tape, about 3 turns, around the thread, NOT the olive, in the right direction so that it does not unwrap as you tighten the joint,

 

Make sure the olive is seated correctly (don't rely on the tightening process) and tighten up.

 

Use no gunk of any sort. You will be much happier if you come back to work on the joint in the future. LSX is brilliant and I use on waste systems provided it won't show. It goes yellow with age. But you don't need it on compression joints. Open tubes go off quite quickly.

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Wrap PTFE tape, about 3 turns, around the thread, NOT the olive,

 

I agree with most of what you say except this. I can think of no rationale for putting PTFE tape on the thread of a compression joint. The thread plays no part in the water seal.

 

You have obviously thought about it though. Why do you think PTFE on the thread makes a difference?

 

Mike

Edited by Mike the Boilerman
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I agree with most of what you say except this. I can think of no rationale for putting PTFE tape on the thread of a compression joint. The thread plays no part in the water seal.

 

You have obviously thought about it though. Why do you think PTFE on the thread makes a difference?

 

Mike

 

Yes, I was going to point that out. There are only two potential leakage paths - between the inside of olive and the pipe and between the cone of the olive and the fitting. No other part of the fitting seals anything

 

Richard

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I agree with most of what you say except this. I can think of no rationale for putting PTFE tape on the thread of a compression joint. The thread plays no part in the water seal.

 

You have obviously thought about it though. Why do you think PTFE on the thread makes a difference?

I kind of touched on it in post #12, it reduces the total force needed to tighten the fitting, and makes it easier to feel when the olive is starting to 'nip up' on the pipe.

 

So indirectly it can help avoid under tightening and over tightening the fitting, thereby giving a better seal.

 

See also post #11 to #14 in this thread:

 

http://www.canalworld.net/forums/index.php?showtopic=20520&view=findpost&p=338242

 

cheers, Pete.

~smpt~

Edited by smileypete
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I agree with most of what you say except this. I can think of no rationale for putting PTFE tape on the thread of a compression joint. The thread plays no part in the water seal.

 

You have obviously thought about it though. Why do you think PTFE on the thread makes a difference?

 

Mike

 

I understand what you are saying and I completely agree with you. It makes no sense to me either - but it works!

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