A question of PTFE tape

[blackrose]

I'm doing a bit of backboiler plumbing and as far as I can see the outlets are straight threaded male pipes.

 

I've used a couple of wraps of gas PTFE tape because it's thicker and easier to use, but it's not staying in place and is just getting mashed between the threads.

 

 

Is this ok - will it still seal the threads, or is it supposed to stay wrapped intact around the threads?

 

Am I using too much tape or should I just use ordinary PTFE tape instead?

[Mooresey]

I have used PTFE paste in the past for water pipes and that worked a treat for stopping leaks. Not sure if you can use it for gas though.

[bizzard]

Are you winding the tape on in the correct direction, clockwise on a normal righthand thread, the same direction as a nut would turn to do it up, and stretch it quite a bit as you wind.

Edited September 6, 2012 by bizzard

[blackrose]

I have used PTFE paste in the past for water pipes and that worked a treat for stopping leaks. Not sure if you can use it for gas though.

 

There is a product called gas PTFE tape which comes on yellow reels and is much thicker than ordinary PTFE. I wouldn't use it for gas on boats, but I've found it works well on water pipe threads (just not this time though!)

 

Are you winding the tape on in the correct direction, clockwise on a normal righthand thread, the same direction as a nut would turn to do it up, and stretch it quite a bit as you wind.

 

Yes, I am.

[BargeeSpud]

Are you winding the tape on in the correct direction, clockwise on a normal righthand thread, the same direction as a nut would turn to do it up, and stretch it quite a bit as you wind.

Thats the way to do it.

[blackrose]

Would I be better off using some Fernox LS-X instead of the PTFE?

 

I have some onboard.

 

http://www.fernox.com/files/Fernox/Content/PDF/English/LS-X.pdf

[Justme]

When you test fitted that union was it very loose / sloppy?

 

If so then the tape wont take all that play up.

 

I think you might have some sort of thread mis match.

 

The boiler stub looks like a standard straight BSP but the fitting could be a tapered thread.

[bizzard]

Would I be better off using some Fernox LS-X instead of the PTFE?

 

I have some onboard.

 

http://www.fernox.com/files/Fernox/Content/PDF/English/LS-X.pdf

That looks alright, you could wind some plumbers hemp onto the thread or even cotton to give it more body.

[nb Innisfree]

Can't remember what it's called but instead of PTFE I use some sort of white string stuff, made by Loctite prob?

 

Otherwise try the thinner PTFE tap and use more turns, I tend to have the same issues with the gas stuff.

 

ETA: Loctite 55

Edited September 6, 2012 by nb Innisfree

[blackrose]

When you test fitted that union was it very loose / sloppy?

 

If so then the tape wont take all that play up.

 

I think you might have some sort of thread mis match.

 

The boiler stub looks like a standard straight BSP but the fitting could be a tapered thread.

 

If it's tapered it's a very slight taper. I can't see any taper at all.

 

It wasn't a loose or sloppy fit.

[bizzard]

If it's tapered it's a very slight taper. I can't see any taper at all.

 

It wasn't a loose or sloppy fit.

If the boilers stub is parallel a thinnish backing nut is really meant to be used which with a fibre washer would back up onto your elbow, but it doesn't really matter, you should get a good seal with the stuff you have but i would use a bit of hemp or cotton on the thread to beef it up. I still use boss white and hemp for similar fittings.

[bag 'o' bones]

I've used hermatite red on locomotive steam fittings that refused to seal.

Edited September 6, 2012 by bag 'o' bones

[Gibbo]

Isn't that the wrong pipe fitting? Yours should have a washer like this...

 

 

In hich case the PTFE is doing nothing.

[MtB]

It doesn't look to me as though you've used enough gas PTFE tape, or wound it on tight enough.

 

Yes, for improved likelihood of your joints being 100% watertight, wipe some LSX on the inside thread of the brass fitting before screwing it onto the PTFE'd male thread, i.e. use both.

 

 

Mike

 

Or yes, use a tap connector like Gibbo suggests. What size thread is it?

Edited September 6, 2012 by Mike the Boilerman

[bowten]

As Gibbo suggests and use high temp sealant around the threads.

[nb Innisfree]

Tap connector is ok provided the end of the male stub is square and smooth for washer to seal which I doubt it is.

[smileypete]

Would I be better off using some Fernox LS-X instead of the PTFE?

 

I have some onboard.

 

http://www.fernox.com/files/Fernox/Content/PDF/English/LS-X.pdf

Yeah, that's fine, 'Suitable for use from below freezing point to above boiling point of water'

 

http://www.fernox.com/files/Fernox/Content/PDF/English/LS-X.pdf

 

Personally I'd put it on the male back boiler stub thread then screw the female brass thread on. That way any excess will be squeezed outside the fitting but not inside where blobs of it could come loose and do a mischief.

 

As long as it's assembled reasonably soon after applying, then left alone during/after setting it'll do great.

 

cheers, Pete.

~smpt~

[blackrose]

The gas PTFE seems to have sealed it ok. I took the fittings off and rewound some fresh PTFE over the threads. I just finished the rest of the plumbing and filled it up. The only leaking joints were the 22mm compression fittings. Those things need to be done up tight!

[blackrose]

Isn't that the wrong pipe fitting? Yours should have a washer like this...

 

 

In hich case the PTFE is doing nothing.

 

It's the right fitting. I'm not sure that a fibre washer would seat on the end of a 1" threaded BSP pipe. Don't sealing washers usually come with smaller diameter fittings like the tap connector you've pictured?

Edited September 7, 2012 by blackrose

[Gibbo]

It's the right fitting. I'm not sure that a fibre washer would seat on the end of a 1" threaded BSP pipe. Don't sealing washers usually come with smaller diameter fittings like the tap connector you've pictured?

 

I don't know, I've seen some huge ones. Relying on a thread for sealing doesn't seem too secure to me.

[blackrose]

I don't know, I've seen some huge ones. Relying on a thread for sealing doesn't seem too secure to me.

 

No it's not ideal unless it's a tapered thread, but I don't think the pipe ends would seal on a narrow washer either. Anyway, the PTFE seems to have sealed it.

[the grinch]

The gas PTFE seems to have sealed it ok. I took the fittings off and rewound some fresh PTFE over the threads. I just finished the rest of the plumbing and filled it up. The only leaking joints were the 22mm compression fittings. Those things need to be done up tight!

 

 

no they don't as you will compress the olive too much and damage the pipe! simple trick is to tighten enough to get the olive compressed enough not to move, undo the nut wrap 2 turns of gas ptfe over the olive and reassemble tighten sufficiently to stop leakage.

 

only bodgers like British Gas use LSX its crap in my opinion boss white or even gas seal are far better products.

[blackrose]

no they don't as you will compress the olive too much and damage the pipe! simple trick is to tighten enough to get the olive compressed enough not to move, undo the nut wrap 2 turns of gas ptfe over the olive and reassemble tighten sufficiently to stop leakage.

 

only bodgers like British Gas use LSX its crap in my opinion boss white or even gas seal are far better products.

 

With plastic pipe I'd agree with you, but I don't think you're going to damage 22mm copper pipe with an olive. The olive would go first. Anyway, I tightened the leaking compression fittings and they stopped leaking.

 

Olive and PTFE? I didn't think olives were designed to be used with PTFE. Surely an olive should seal by itself?

Edited September 7, 2012 by blackrose

[RLWP]

With plastic pipe I'd agree with you, but I don't think you're going to damage 22mm copper pipe with an olive. The olive would go first.<snip>

 

It doesn't. You just end up squashing the pipe

 

Richard

[bizzard]

When a new compression fitting leaks after fitting its usually one of three things causing it.

Over or under tightening it or the pipes not properly inline with the fitting (at a bit of an angle to it)and maybe have been slightly forced in or not pushed fully home putting stress on the olive and pipe.