PTFE tape on compression fittings

Discussion in 'Plumbers' Talk' started by furious_customer, Jul 10, 2018.

  1. furious_customer

    furious_customer Active Member

    I have always used 3 to 4 winds of PTFE tape on the threads of compression fittings, but I have just seen a youtube video where they put the ptfe tape over the olive (already compressed I think).

    What is the correct/best way to use PTFE tape with compression fittings?
  2. dobbie

    dobbie Well-Known Member

    Use none,there is no need at all for PTFE on compression fittings,it is for going on threads.
    If you want, use a bit of boss blue/white on the fitting depending what it is being used for.
    It looks terrible seeing a compression fitting with ptfe tape sticking out of it or wrapped on the pipe.
    Last edited: Jul 10, 2018
    Heat likes this.
  3. furious_customer

    furious_customer Active Member

    which threads?
  4. Dr Bodgit

    Dr Bodgit Well-Known Member

    PTFE is used on the boss of lockshield/TRV radiator fittings, I put about 15 wraps on mine.

    As dobbie says, just add a bit of boss white or similar on the fitting, over the olive. It shouldn't be needed but adds a touch of insurance.
  5. dobbie

    dobbie Well-Known Member

    An example
    [​IMG]You would put tape on the thread and a bit of paste on the compression end.
  6. furious_customer

    furious_customer Active Member

    This is a compression fitting, right? A straight-coupler?
    I have always put the tape on the threads, but was interested to see this video putting it over the olive, which does seem to make sense.
  7. Joe95

    Joe95 Well-Known Member

    There's no need to put anything on the thread, the seal is made between the olive and the end of the compression fitting. The thread serves no other purpose but to provide a way of tignting the nut. Threaded connectors however, like rad bosses or garden taps, require PTFE on the thread as there is no sealing mechinism (like a washer on a flexi, or an olive in a compression fitting).

    Using them on new fittings is not great, you are introducing something which is not required. If they leak after repressuring, a quick nip up should seal it.

    Having said all that, if I undo any compression fittings and they've been done up too tightly, I will wrap the olive in PTFE. I like to think of PTFE being a 'last resort' item for compression fittings and olives.
    furious_customer likes this.
  8. furious_customer

    furious_customer Active Member

    thanks guys
  9. Dr Bodgit

    Dr Bodgit Well-Known Member

    Quick video
  10. rogerk101

    rogerk101 Well-Known Member

    The only benefit I can see of using PTFE tape anywhere near a compression fitting is as a lubricant. It is most certainly not used or even desirable as a sealant.
    However, far better than PTFE as a lubricant is to use the real lubricant intended for compression fittings, and our hosts and many of their competitors stock it.
    As an FYI, I have seen quite a few situations where too much PTFE has actually burst the very brass fittings they were intended to be sealing.
    Pollowick likes this.
  11. furious_customer

    furious_customer Active Member

    This is the video that made me ask the question! Watch the bit were he adds PTFE tape over the olive!
  12. Dr Bodgit

    Dr Bodgit Well-Known Member

    Yes...on the olive not the thread.

    Never used PTFE tape on compression fittings myself.
  13. retiredsparks

    retiredsparks Well-Known Member

    So, what have we learnt so far.
    Some say yes, some say no.
    Some say use a boss white on the olive.(which indicates a distrust of the fitting ?)
    Some say the PTFE is a 'lubricant' for the threads (no)..altho it does have a coefficient of friction of about 0.02 (the same as wet ice on wet ice)
    Some say not needed (sometimes it is) and is sloppy.(2 inches of water all over the floor is "sloppy")
    I say with the ever reducing quality of pipe and brass fittings it "may" be useful on remade compression fittings and new.
    In the video the pipe is not even clean !!!!
    What a wonderful advisory video.(not)
    Also, referring back to a previous post........most of the PTFE on threads is not in any way useful or performing any function....when it is pushed to the back of the fitting and creates a huge why use so many wraps ?
  14. Dr Bodgit

    Dr Bodgit Well-Known Member

    Up until recently I didn't use anything on compression fittings, and there should be no need for anything.

    I see boss white or similar as a bit of insurance, does no harm to add a bit and as I have it, I add a smear.

    PTFE is an escalation where the fitting is not water tight and needs some remedy. Should not be needed, is rarely needed but might fix a problem if there is one.

    Oh and by the way, happy birthday Nikola.
  15. Heat

    Heat Well-Known Member

    Ptfe tape is only for male threads.
    The threads on end of fittings where the pipe goes in is only for the nut to pull the fitting and pipe with olive together.
    If a joint was to leak, the ptfe on the thread at pipe end wouldn’t seal the joint anyhow, as the water would simply go between the nut and the pipe.
    Any job I see ptfe on the wrong threads I remove all the work as clearly installed by a complete diyer.
    Ptfe tape wrapped around an already compressed olive will help seal the joint, but paste is better and essential to prevent small leaks. Microscopic leaks occur if the joints aren’t pasted and the seized nuts or white corrosion on the brass threads is proof of this. V2 Lube is good and does potable water.
    The rubbish standard brass fittings and olives we have nowadays do need extra sealant rather than depending on the olive
  16. ajohn

    ajohn Active Member

    I reckon that olives do need some sort of joint compound. I see it as more of a lubricant than anything else. Some even have ptfe in them. It makes it easier to compress the olive. Frome what I have seen after undoing fittings that were fitted 10 years plus ago the stuff dries out so probably doesn't really add any sealing.

    Pfte tape - I haven't used it but had some people in to do some work on gas pipes. All of that was soldered. I also needed a cold water pipe feed added to an existing pipe. They used 2 wraps of standard ptfe tape over the olives. Seems this is what they usually do on water as it's a less messy job.

    People can anneal bras olives if they want. Heat to dull red and chuck into cold water. My father used to do this as he thought that fully annealed brass had to be better - he often had a lot of trouble getting them to seal so maybe they are best left as they come or maybe it would be an improvement if some sort of lubricant is used.

    retiredsparks likes this.
  17. PhilSo

    PhilSo Active Member

    I believe dousing in cold water hardens the metal.
    Leaving to cool slowly anneals the metal.
    IIRC. :rolleyes:

    DIY womble, retiredsparks and seneca like this.
  18. ajohn

    ajohn Active Member

    Not brass, it has to be quenched to anneal it.

  19. PhilSo

    PhilSo Active Member

    I guess IDRC. :rolleyes:
  20. PhilSo

    PhilSo Active Member

    Nagged me a bit. Don't like to think the memory is failing completely yet. So Wikipedia.
    In the cases of copper, steel, silver, and brass, this process is performed by heating the material (generally until glowing) for a while and then slowly letting it cool to room temperature in still air. Copper, silver[1] and brass can be cooled slowly in air, or quickly by quenching in water, unlike ferrous metals, such as steel, which must be cooled slowly to anneal. In this fashion, the metal is softened and prepared for further work—such as shaping, stamping, or forming.


    PhilSo (redeemed)

    Funny old weld innit :D

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