Boss White or PTFE?

[Araucaria]

I've got a number of brass BSP plumbing joints to make, mostly 3/4" but some 1" ones, and the matching pieces are all a pretty slack fit in their raw (untreated) state.

What do others recommend: lots of PTFE tape, or Boss White and hemp?

Is there some form of professional guidance on which should be used where?

[just john]

Blimey, long time since I saw boss white & hemp, which I recall as for steel, perhaps leftovers were used on brass, but I'd say PTFE.

[tonyv]

I've always successfully used PTFE tape, but when I had French "professionals" install my central heating recently, I was surprised to see that they use "stuff". It certainly wasn't white, more a dark grey, and the flossy stuff probably wasn't hemp. I think "stuff" probably works out cheaper than PTFE, and is probably easier to apply. It's messy, though.

[Araucaria]

The brico-places nearly all sell hemp (I am fairly sure it really is hemp) and whatever the French equivalent of Boss White is.  There's a different formulation for drinking water, but Boss White is pretty well grey nowadays, and perhaps it always was. Maybe it was a Mr White, who happened to own the company, who invented it?

[Nick Trollope]

I was always told that PTFE should only be used on threads that were meant for PTFE tape (with a broken surface to the thread).

We always use filasse and pâte (for that is what it is) for all such joints.

[Gluestick]

In order for PTFE tape to work successfully, it needs considerable contact interference and this pressure on the mating thread forms: which deforms the plastic into a solid mass which self-heals.

Very loose fittings should be mated using some form of "Plumber's Mate" (Modern equivalent of white lead putty) and fibre.

Interestingly, one can now buy liquid PTFE: I personally, however, would still use plumber's putty and fibre.

I've seen some appalling joints made with bundles of PTFE: presumably on the old "The bigger the blob: the stronger the job!" basis.

They still tended to weep, however.

[Araucaria]

Thanks everyone.

In the end it was mostly Boss White and hemp (though having done some research I think it's probably flax, aka tow, rather than hemp). This made a pretty good joint. I suspect a thick enough layer of PTFE tape would have worked too, but on the couple I tried with PTFE, even after 20 or more turns of tape the threads screwed all the way down without making a decent seal.

A couple of the compression fittings seeped a little bit, and elsewhere I had found a suggestion that one or two turns of PTFE tape on the outside of the olive (not on the threads) might help. And it did.

[AnOther]

Compression fittings should not leak nor should there be any need for 'help' be that from PTFE tape, plumbers mate, hemp, or WHY.

[Chancer]

Plenty of plumbers say this, and a not inconsiderable quantity of compression fittings dont seal unless they are gorilla'd some still weep after that, Why? _ Just take a close look at the machining on many fittings.

Using PTFE tape on all olives liek many plumbers do avoids having to overtighten the fitting.

I prefer to avoid compression fittings wherever I can.

[Northender]

I thought the French still used crin de cheval with their pate a joint?

[Araucaria]

I don't like compression fittings either, but it's a solar heating circuit and they (the "experts") recommend compression fittings on the hot part of the circuit. None of my soldered joints leaked. I'm not a professional plumber, but it was only 4 out of 22 compression joints that were a problem. And the tape definitely cured three of these, maybe all four (I'll find out shortly).

But in general I'd agree: compression fittings don't need tape. The 18 good compression joints didn't have any. What went wrong with the other four I really can't say.

[BIG MAC]

I almost exclusively use PTFE

[Gluestick]

[quote user="Araucaria"] The 18 good compression joints didn't have any. What went wrong with the other four I really can't say.

[/quote]

Bad tolerances on machining and production.

The Olives are pressed by "Upsetting" from a collar: the joining section needs careful machining of the face of joint: as does the nut: capstan work using CNC machines.

Bit of swarf or dirt in the tooling for the olive and it's out of shape.

When the tool is worn towards the end of a run, the faces are not properly symmetrical.

A compression fitting works by squashing the olive onto the pipe: and forcing the contact faces down onto the bottom face and into the identical contact face of the nut, by the compressive force exerted by the screw thread.

If any bit of the three part assembly is out of spec. then it will leak.

Guaranteed.

[Dave&Olive]

Hi Ok

  I worked in a brewery for over 20 years as a fitter , you can imagine how many pipes there was... black iron / galv / copper / and s  ...steel  the day   P T F E tape arrived my Boss white went  in the skip ....  Wrexham Lager alas no more

                       Dave

[BIG MAC]

Sorry,

My previous posting was rather brief as I had no sooner started writing it than I remembered I had to plumb our downstairs bath in!...I was half way through and forgot! lol