Weeping compression fittings

[Jupiter01]

After some of your wisdom on how the above is handled please.

On a few occasions, I have used compression fittings (tried to follow all the suggested advice on fitting these) and after nipping them up, I have dried any residual water, used a torch to inspect if there is any leak. I have then waited and inspected this for a further 10-15 minutes using blue roll to detect any leak. It has been fine at this stage (no leaks) but when I return a few hours later (or the next day) I discover that they are weeping.

How do people verify theirs and ensure this situation doesn’t occur. I imagine it’s very important when you are onsite and may not be at the same site on the next day.

Thanks in advance.

 

[terryplumb]

Starts with the preparation , pipe in good condition and smoothe ,olive in good condition. Then experience of how much to tighten up,coupled with a smear of LSX on the olive.

 

[MeldrewsMate]

Clean the pipes.
Use jointing compound; mine is Jet Blue, but others are available. PTFE is NOT for compression fittings.
Hand tighten, then up to 1/2 a turn (3 flats) with spanners; always supporting the fitting to avoid stressing the other end.
Overtightening will partially crush the pipe and lead to leaks.

Could you be confusing cold pipe sweating with a weeping joint?

All the above refers to copper pipe and brass fittings, brass or copper olives.

 

[Deleted member 292770]

I use boss white on heating joints and blue hawk on potable fittings. and a little on the threads too as a bit of lube.

 

[Wayners]

I put tiny tiny smear of vaseline on thread. Can do up hand tight and won't leak but don't try.
The grinding and grabbing of thread means you can't tell so easy how tight nut is, so I have a theory that joint compound, silicone and other products just lubricates the thread which helps it tighten smoothly vs grabbing and uneven turning.
Over tighten is most common problem causing leak.
Chrome plating on threads is rough.

 

[Jupiter01]

Clean the pipes.

How should this be done and presumably the olive area of the pipe? Is it also essential that the pipe is dry?

PTFE is NOT for compression fittings

I understood that PTFE wrapped around an existing olive can help the join. Appreciate that it is not required for a new fitting.

Over tighten is most common problem causing leak.

If the joint is leaking due to over tightening, how is this rectified?

Thanks for all your suggestions

 

[MeldrewsMate]

I understood that PTFE wrapped around an existing olive can help the join. Appreciate that it is not required for a new fitting.

If the joint is leaking due to over tightening, how is this rectified?

If PTFE tape is adequate for wrapping around an old olive, then why not wrap gaffer tape around a leaking pipe

If the pipe has been distorted by overtightning then that section must be replaced with good pipe.

 

[Madrab]

My rule of thumb for compression fittings - All pipe should be clean and dent/necking/corrosion free and I always use copper olives, any brass ones head for the bag.

New fitting and olive - nothing needed - hand tight then 1/2 turn
Reusing old fitting with new olive - clean fitting's mating surfaces with green pad/120grit - hand tight then 1/2 turn
Reusing old fitting and olive - Clean mating surfaces and olive same as previous - 1 wrap of gas PTFE tape around the olive - hand tight then 1/2 turn, may need revisited and another nip if weeping.

Hasn't failed me yet.

If the old olive/pipe is damaged due to over-tightening then the olive needs to be removed and the pipe checked for necking, if pipe ok then just a new olive, if pipe is necked then section of pipe needs replaced.

 

[DP]

My rule of thumb for compression fittings - All pipe should be clean and dent/necking/corrosion free and I always use copper olives, any brass ones head for the bag.

New fitting and olive - nothing needed - hand tight then 1/2 turn
Reusing old fitting with new olive - clean fitting's mating surfaces with green pad/120grit - hand tight then 1/2 turn
Reusing old fitting and olive - Clean mating surfaces and olive same as previous - 1 wrap of gas PTFE tape around the olive - hand tight then 1/2 turn, may need revisited and another nip if weeping.

Hasn't failed me yet.

If the old olive/pipe is damaged due to over-tightening then the olive needs to be removed and the pipe checked for necking, if pipe ok then just a new olive, if pipe is necked then section of pipe needs replaced.

Thanks Rab, same here. Rocket Science it is not when making a compression joint. Have not used sealing compounds since I was a wee boy. Hate the stuff- not needed to use it since god knows when. If push comes to a shove, wraps of ptfe tape suffice. If it still leaks or weeps, something wrong somewhere- undo and repair

 

[Madrab]

Thanks Rab, same here. Rocket Science it is not when making a compression joint. Have not used sealing compounds since I was a wee boy. Hate the stuff- not needed to use it since god knows when. If push comes to a shove, wraps of ptfe tape suffice. If it still leaks or weeps, something wrong somewhere- undo and repair

Spot on @DP, that's the way I look at it too ... that and the tightening of the fitting becomes an experience thing. With me it's usually the squeak point, unless there's tape on it.

 

[BlueLoo]

Don't understand the engineering logic regarding the use of goop, tapers, thread lock, ptfe, locktite, or anything on a compression fitting.

I know plumbers swear by whatever they have used for years, but, putting anything in the way of the olive and its fitting is in my understanding completely counter productive.

I think its a cross over from taper thread fittings where the seal is the thread.

Ptfe tape is for threads i believe. Both to lubricate the connection and to seal. It's a modern day hemp replacement.
Ptfe liquid is a lazy version of the tape.
Boss white is for taper threads as well.

My house was plumbed with compression fittings and hemp/boss white.

If i could find the plumber who did that, I'd throttle him.

I've replumbed most of it since with compression fittings and never had a leak or weap, unlike the previous install.

As per the poster above, i have used a little vaseline on the threads on stiff (cheap) fittings to help me torque them up. Thats it.

If anyone can give me a reasonable engineering justification for using crap on a compression fitting, I'm all ears.

 

[oilhead]

Each to his own. Where old joints are remade, a turn of ptfe tape on the olive allows the tightening to seal any tiny imperfections in the olive or pipe.

 

[BlueLoo]

Each to his own. Where old joints are remade, a turn of ptfe tape on the olive allows the tightening to seal any tiny imperfections in the olive or pipe.

No it doesn't.

You just place contamination between the sealing surfaces which get crushed out on tightening.

Ptfe is highly inelastic and a terrible gasket material.
You also shouldn't be taping anything near the internal flow path as bits break off and move to places they shouldn't be.

 

[BlueLoo]

https://www.pegleryorkshire.co.uk/M...7875422_Prestex_installation_instructions.pdf

The correct method.

 

[Deleted member 292770]

Don't understand the engineering logic regarding the use of goop, tapers, thread lock, ptfe, locktite, or anything on a compression fitting.

I know plumbers swear by whatever they have used for years, but, putting anything in the way of the olive and its fitting is in my understanding completely counter productive.

I think its a cross over from taper thread fittings where the seal is the thread.

Ptfe tape is for threads i believe. Both to lubricate the connection and to seal. It's a modern day hemp replacement.
Ptfe liquid is a lazy version of the tape.
Boss white is for taper threads as well.

My house was plumbed with compression fittings and hemp/boss white.

If i could find the plumber who did that, I'd throttle him.

I've replumbed most of it since with compression fittings and never had a leak or weap, unlike the previous install.

As per the poster above, i have used a little vaseline on the threads on stiff (cheap) fittings to help me torque them up. Thats it.

If anyone can give me a reasonable engineering justification for using crap on a compression fitting, I'm all ears.

It’s just your opinion that it’s crap.....lubrication, and a fail safe against increasingly poor quality. when you dismantle hundreds of chrome brass steel copper fittings it becomes apparent that the twist effect on a compression fitting can sometimes drag on the threads and more importantly on the olive. . more common in recent years due to everything being made cheaper .I suppose it’s fine if you have one or two that you can keep an eye on but when there’s a potential 50 say olives in a heating and hot/cold system the plumber needs to know that they won’t be causing damage to property and getting calls back to weeping joints.