Leak on compression fitting

[Steve Manc]

Hi

We have a small leak on a 15mm  compression water fitting underneath a gas boiler. Boiler Engineer doesn't want to apply move pressure to untighten the nut just in case he causes damage. The boiler is 15 years plus years old. We have applied WD-40 each day for 5 plus days with little success.

Has anyone used a putty with any success to seal a leak or something different?

 

I am considering applying the following to the outside of the joint:

JB Water Weld Putty Quickly Sets Under Water Fuel & Oil Resistant.

 

Please see screenshot of the type of compression fitting the leaking from the top.

 

 

 

 

Edited November 14, 2024 by Steve Manc
Grammar

[MtB]

Nothing applied to the outside of a compression fitting will stop a leak. 

 

You really need to turn the water off, dismantle the joint and I'd suggest a turn or two of PTFE tape tightly wrapped around the olive, then reassemble and tighten it up again. 

 

Your boiler engineer is being prudent as sometimes just tightening a compression fitting makes it leak faster. Chrome fittings are notorious for leaking if assembled dry with no sealant such as PTFE over the olive. 

 

 

[Steve Manc]

MtB

 

Thanks for the reply 

 

I was present when he tried. Said he was worried if he apply more pressure, to secure it or loosen it, it may damage the fitting it's secured to.

[LEO]

WD40 is good, but the wrong product, you need a good penetrating oil, PDQ is one and there are several more available now. spray or paint a small amount onto the fixing.

 

WD40 is a water repellent and lubricant, a great product..............

[1st ade]

8 hours ago, MtB said:

Chrome fittings are notorious for leaking if assembled dry...

Now he tells me (having just replaced a heated Towel Rail with Mrs 1st Ade saying 'Oh, those Chrome fittings look much nicer...')

[nicknorman]

9 hours ago, MtB said:

Nothing applied to the outside of a compression fitting will stop a leak. 

 

You really need to turn the water off, dismantle the joint and I'd suggest a turn or two of PTFE tape tightly wrapped around the olive, then reassemble and tighten it up again. 

 

Your boiler engineer is being prudent as sometimes just tightening a compression fitting makes it leak faster. Chrome fittings are notorious for leaking if assembled dry with no sealant such as PTFE over the olive. 

 

 

Agreed but note that he was commenting on trying to untighten (aka loosen) the fitting, presumably to gain access to the olive.

 

i would say that you have to apply whatever force is necessary to undo it, BUT you need to hold the fitting with eg mole grips to stop it trying to turn. You align the mole grips along the fitting in the same axis as the spanner on the nut, that way you don’t have to grip it too hard. If you do end up damaging (ie badly scratching) the fitting, so what? They are not expensive. Although PTFE tape on the threads is not the way to attempt to seal a compression fitting leak, PTFE tape has a lubricating effect as well (although liquid PTFE is probably a better option) and a turn on the threads might help avoid seizure next time.

Edited November 15, 2024 by nicknorman

[Tony Brooks]

I noticed that the fitting shown have no flats on the body to allow you to put a spanner on them to take the reaction to the undoing, so, as Nick says, grips. I use water pump/gland nut grips with the tips pf the jaws on the flats of the nut and set so the body of the fitting is held but the rest of the jaws.

[Ronaldo47]

Assuming there is room, I use a smooth-jawed adjustable spanner on the other arm of the elbow, aligned with its jaws along the axis of the other branch.

 

A text book on gas fitting written by the old North Thames Gas Board for  HNC students, emphasised that tools with teeth, such as Stillson wrenches and pipe grips, should never be used on chromium-plated fittings.

Edited November 15, 2024 by Ronaldo47
Typos

[nicknorman]

2 minutes ago, Ronaldo47 said:

Assuming there is room, I use an adjustable spanner on the other arm of the elbow, aligned with its jaws along the axis of the other branch.

 

A book on gas fitting written by the old North Thames Gas Board for  HNC students, emphasised that tools with teeth, such as Stillson wrenches and pipe grips, should never be used on chromium-plated fittings.

Agreed, and I have a large adjustable spanner which I can use for the purpose. But most people only have mole grips etc. Scratching the chrome is not exactly disastrous for water plumbing, but I guess for gas there is a greater risk that cracking the fitting causes a serious problem.

Edited November 15, 2024 by nicknorman

[Tonka]

2 hours ago, LEO said:

WD40 is good, but the wrong product, you need a good penetrating oil, PDQ is one and there are several more available now. spray or paint a small amount onto the fixing.

 

WD40 is a water repellent and lubricant, a great product..............

WD40 is actually a brand name and you will find that they do WD40 Bike Degreaser, WD40 Penetratting Oil and the usual WD40 water displaysor to name a few 

Edited November 15, 2024 by Tonka

[smiler]

1 hour ago, nicknorman said:

Agreed but note that he was commenting on trying to untighten (aka loosen) the fitting, presumably to gain access to the olive.

 

i would say that you have to apply whatever force is necessary to undo it, BUT you need to hold the fitting with eg mole grips to stop it trying to turn. You align the mole grips along the fitting in the same axis as the spanner on the nut, that way you don’t have to grip it too hard. If you do end up damaging (ie badly scratching) the fitting, so what? They are not expensive. Although PTFE tape on the threads is not the way to attempt to seal a compression fitting leak, PTFE tape has a lubricating effect as well (although liquid PTFE is probably a better option) and a turn on the threads might help avoid seizure next time.

PTFE tape around the olive will probably help as a temporary fix.

As said above, PTFE on the threads won't do much to help the leak.

 

Proper fix is try to tighten it a bit more or a new fitting with new olives (if damaged) if there is enough length in the pipework.

Does the fitting have to be chrome?

 

 

 

 

Edited November 15, 2024 by smiler
***Edited for spilling misteak.***

[Tony Brooks]

Just now, smiler said:

PTFE tape around the olive will probably help as a temporary fix.

As said above, PTFE on the threads won't due much to help the leak.

 

Proper fix is try to tighten it a bit more or a new fitting with new olives (if damaged) if there is enough length in the pipework.

Does the fitting have to be chrome?

 

AND as long as past gorilla tightening has not collapsed the pipe under the olive. With no history, I would prefer to dismantle it to see if the pipe has collapsed or if the olive is on askew. If so, just tightening it a bit more may well make the situtaion worse.

[smiler]

Just now, Tony Brooks said:

 

AND as long as past gorilla tightening has not collapsed the pipe under the olive. With no history, I would prefer to dismantle it to see if the pipe has collapsed or if the olive is on askew. If so, just tightening it a bit more may well make the situtaion worse.

👍

[nicknorman]

Of course one problem is that modern olives are made of some brass type thing to save money. Much harder than the copper pipe. Copper olives are better if you can get them.

[Batavia]

5 minutes ago, nicknorman said:

Of course one problem is that modern olives are made of some brass type thing to save money. Much harder than the copper pipe. Copper olives are better if you can get them.

Unfortunately not all copper olives are created equal - I recently had some, from a reputable supplier, which were so thin that I couldn't get a seal on a few compression fittings without using LS-X on the olive.

[alan_fincher]

15 minutes ago, Batavia said:

Unfortunately not all copper olives are created equal - I recently had some, from a reputable supplier, which were so thin that I couldn't get a seal on a few compression fittings without using LS-X on the olive.

 

I may have missed it, but think this is probably the first mention in the thread of Fernox LS-X.  I'm well aware that compression joints should need no sealant and/or tape, but actually I have found LS-X very effective in sealing compression joints that are not 100% leak-proof.

 

However LS-X can only help if you are unable to undo the joint with no further damage.  In this case it sounds like that has been declared risky?

I'm not aware of much that can be applied externally to make the damaged joint watertight -  a number of things might work, but they are far from guaranteed.

[Batavia]

11 minutes ago, alan_fincher said:

However LS-X can only help if you are unable to undo the joint with no further damage.  In this case it sounds like that has been declared risky?

I think that you mean "able" not "unable"!

LS-X only works if you can smear it round the olive before assembling the fitting, as I think you implied.

Chris

[jacko264]

I use ptfe. Tape on joints like that but could the leak be above the joint and running down the pipe to the joint ?

[alan_fincher]

1 hour ago, Batavia said:

I think that you mean "able" not "unable"!

LS-X only works if you can smear it round the olive before assembling the fitting, as I think you implied.

Chris

 

Apologies Chris - yes my mistake.

 

Should have read....

 

However LS-X can only help if you are able to undo the joint with no further damage.  In this case it sounds like that has been declared risky?

[Ex Brummie]

Is the leak on a mains feed fitting or a heating circuit?  If somewhere you can't isolate and repair properly, a self amalgating tape might provide a temporary fix. You could even apply it over a smear of LS-X.

[David Schweizer]

If the joint has started to leak after 15 years of reliable service, there is a possibility the the original plumber dressed the olive with boss white, which has degraded over the years. I recently had exactly this problem with a washing machine tap in my house, I removed the fitting, cleaned all the boss white off and polished the olive gently with some ultra fine grade wire wool. The original tap was a bit damaged during the dismantling, so I replaced it with a compatible new one and reassembled the joint dry, using the original olive and compression nut. So far there has been no sign of any leaking.

 

 

Edited November 15, 2024 by David Schweizer

[nicknorman]

6 minutes ago, David Schweizer said:

If the joint has started to leak after 15 years of reliable service, there is a possibility the the original plumber dressed the olive with boss white, which has degraded over the years. I recently had exactly this problem with a washing machine tap in my house, I removed the fitting, cleaned all the boss white off and polished the olive gently with some ultra fine grade wire wool. The original tap was a bit damaged during the dismantling, so I replaced it with a compatible new one and reassembled the joint dry, using the original olive and compression nut. So far there has been no sign of any leaking.

 

 

Yes in my not-so-humble opinion as an amateur plumber, an olive compression fitting is designed to seal without any extra goo. Extra goo usually just causes problems or was used to cover up a bodge eg pipes not aligned properly, too short etc!

[Peugeot 106]

According to Wade “tape or sealing compounds are not required to make a joint”. So Wade just say they are not necessary not that you mustn’t use them. I never used them in the past but recently I’ve been told by plumbers to use them. Recently I cured a compression fitting water leak by dismantling and applying tape. Confusing eh?
They are not a good idea in fuel lines beyond the filter though as the bits can get in the injectors as I understand it.

[jacko264]

If it’s easy to get to why not drain the water and fit a new fitting and remove old olives  too

or if copper pipe get a solder joint fitted by a Plummer if needed 

[MtB]

24 minutes ago, Peugeot 106 said:

According to Wade “tape or sealing compounds are not required to make a joint”. So Wade just say they are not necessary not that you mustn’t use them. I never used them in the past but recently I’ve been told by plumbers to use them. Recently I cured a compression fitting water leak by dismantling and applying tape. Confusing eh?
They are not a good idea in fuel lines beyond the filter though as the bits can get in the injectors as I understand it.

 

Yes compression manus have always maintained this but in practise, the occasional olive has a score, dent or other imperfection in the surface and the same happens to copper tube. In my experience as a plumber I used to assemble them dry as per the manu but pretty quickly learned this is a great way to have about one in 10 or 20 leak. A leak on a new fitting is insanely annoying so I quickly developed the habit of wiping the thinnest film of Bosswhite on the pipe before sliding the olive on, then a further film of Bosswhite on the surface of the olive. This reduced my leak rate on compression fittings to 'never'. LSX works just as well but is messier. PTFE works too but slightly less reliably and takes a bit longer. 

 

The leak rate on chrome or nickel plated fittings assembled dry is probably closer to one in five. 

 

So whether to follow the manu instrutions depends on 1) how lucky you feel and 2) how many joints you will be making.