PTFEed Joints weeping

[DerbyBorn]

Chris Green wrote in news: [e-mail]:

+1

[DerbyBorn]

[e-mail] wrote in news:1a3a4d7f-1f3f-4e6f-b69c- [e-mail]:

Is this a wind up?

[DerbyBorn]

[tabbypurr]

why?

NT

[John Rumm]

Not sure you want to start from there! ;-)

It looks like you have a parallel thread BSP female on a male parallel thread BSP coming out of the tank. That's never going to seal without serious bodgery. The same propably goes for the other two fittings as well alas.

You want a straight tap connector to 15mm compression fitting on the tank, and two bits of copper pipe and an elbow soldered onto the stub of pipe coming out of that Yorkshire fitting to join to it.

[tabbypurr]

e to seal joints. 2 of the joints are 15mm compression tee (with one male e nd, one female end) onto an extension piece, the other is extension piece o nto brass threaded ballcock. 1.5 turns of yellow/gas ptfe tape each, all ne atly in place. I admit to not being clear how the nut would seal to the tee it's on. The one joint done with fibre washer & gloop works fine of course , but I don't think that approach can be used with the other joints.

I realise that now. I have a tube of serious bodgery somewhere. I don't kno w how the previous elbow fitting sealed, it was connected the same way, but I couldn't get it to reseal on the new ballcock.

Too much flammable stuff in close proximity to solder in situ. If I use a s traight compression to connect to a soldered elbow it'll be too long, and t he hand bent pipe only barely manages to be straight enough to fit what's t here now. I guess I'll need to cut the whole area out & start afresh. Fun. Maybe I should try that tube of bodgery first.

NT

[The Natural Philosopher]

Not sure that's true. those soldering mats are very good and a squeegee spray full of water is a handy local extinguisher BUT if you remove everything in the picture you have at one end what looks like a washered joint, and at the other what could be a bog standard olived compression, and the ability to create right angle pipework in between remotely soldered.

[DerbyBorn]

[e-mail] wrote in news:c5ec582a-ff23-49d0-bdde-feffaf309aa0 @googlegroups.com:

It is the sort of fitting that needs washers.

[John Rumm]

Alternative, straight compression on the vertical pipe to connect to a

12" section of plastic pipe. Right angled tap connector on the other end of the plastic pipe. The plastic can then drop down, gently bend into 180deg U shape, and allow the end to come back up to the ballcock with the RA tap connector ready to screw on. That way you don't need to be constrained by the layout of the start and end points or need to solder in situ.

[Harry Bloomfield]

[e-mail] laid this down on his screen :

That is a mess. Those places where I see PTFE poking out, look to me as if they were intended to have a fibre washer fitted between flat faces. You might get PTFE to seal, but only if you can get a regular layer of PTFE around the threads and of just the right thickness, which is unlikely - so it will leak.

[DerbyBorn]

What I was thinking (Looks like a tap elbow)- I would be inclined to take the photo to a decent Plumbers Merchant and get the correct fittings for the job.

Althought PTFE on the tread is not the solution, it should be wound on so that screwing the fitting will tend to tighten the tape - and not push it out.

[andrew.crosland.uk]

The apprentice uses it without thinking. The journeyman avoids it without thinking. The master uses it thoughtfully.

I've never had a problem with it.

[DerbyBorn]

[e-mail] wrote in news:6e07a80c-d49f-477e-ba82- [e-mail]:

It is slapping it onto the treads thinking it will improve the seal that is so wrong. The thread is a clamping mechanism. The olive and cones do the sealing. If these are clean then nothing else is needed. (Stand back for the lubrication comments) Oil could be a good lube, but too often people overtighten from the outset. Mauling a joint!

[John Rumm]

Is anyone suggesting that?

If... alas not something that can always be relied upon in real life. It only takes a deep scratch on a pipe that can't be cut back further, and can't be soldered, or a fitting that must be re-used etc.

Of the many hundreds of compression joints I have made, I have only had to resort to extra steps to get them to seal a handful of times (in fact only two or three that come to mind). Can't see the point in rejecting a solution that works where there is no easy alternative.

It could, but given that most plumbing kits will include PTFE, and it

*is* supremely slippery while also being non messy, there is no harm in using it when necessary IMO.

(or even when not, if you don't enjoy metal to metal squawking - PTFE also makes compression joists very quiet to tighten)

Its actually harder than many imagine - they will usually take fairly serious over tightening before they actually fail unless you distort the nuts.

You are more likely to have a problem with poorly fitting spanners, than too much torque alone.

[newshound]

The bottom line is, this explains why you are getting leaks with PTFE tape only.

You either need a rubber or fibre washer to give an axial seal, or taper threads with sealant, or perhaps some sort of bodge with a setting sealant.

[newshound]

No, you will get lower friction with PTFE.

I still maintain it is the axial force which is important, although it is true this is converted to a radial force by the contact between the cone and the olive. Actually this is an argument for having PTFE tape between the olive and the cone.

[Dave Plowman (News)]

It probably doesn't help, but I'd have done all of that using end feed solder fittings. Which if you take care, never leak.

[newshound]

Or possibly someone who was publishing tribology research in the 1970's and 80's.

[John Rumm]

If one were going to try and get a seal on that with PTFE you would need to be quite careful with the winding of it - basically creating a taper shape[1] on the thread with the tape, so that the "screw in" resistance increases sharply as the stub penetrates further into the female thread.

e.g. you start with say 4 or 5 turns toward the tip of the thread and work up to many more (10 to 20) laid up toward the back of the thread) - winding the tape on "edgeways" so that it folds up helps build thickness faster.

[charles]

Very difficult to get a good joint on a pipe that still has water around. I wouldn't wave a blowlamp near a plastic water tank, either,