Compression joint refuses to seal

Discussion in 'Plumbers' Talk' started by Lynn Dixon, Apr 26, 2017.

  1. Lynn Dixon

    Lynn Dixon New Member

    Hi all,
    I am replacing a shower thermostatic mixer and one of the compression joints to the copper pipe resides to fully seal, have cleaned the pipe and redone several time now always with the same result a very slight leak hot water side only, cold is aboslutley fine and did t need to tighten anywhere near the same to get a good seal. have tightened the offending one as far as I possibly can but nope it still flipping leaks
    I wasn't sure whether to now think about using jointing compound on this joint only (never used before) and whether should itever need replacing again I would then get the compound back off
    Constructive advice greatfull received on what is pricing to be the bane of my life at the mo!
     
  2. Dr Bodgit

    Dr Bodgit Super Member

    Lynn Dixon likes this.
  3. andy48

    andy48 Screwfix Select

    1. Is there at least 5mm of pipe sticking out after the olive. If not you'll need to alter the pipe-work (maybe as simple as pulling the pipe forwards) to ensure there is.
    2. Is the olive firmly attached to the pipe?
    a. If no, then remake joint using a bit of Jetlube or similar as a sealing paste and try again.
    b. If yes, then:
    i. If the pipe has been crushed by the olive being overtightened you may have to replace that bit of pipe, but try 2.b.ii below first.
    ii. Try wrapping 4 to 6 turns of plumbers PTFE tape around the outside of the olive and re-tighten.
     
    Lynn Dixon likes this.
  4. Lynn Dixon

    Lynn Dixon New Member

    Thanks, I'm on the 3rd new olive now so I'm either incredibly olive unlucky or ...
    Think compound is sounding like the way to go, never before had so much trouble with a compression joint, sorry question on the use of compound, just smear on the olive outer or inner too and should I ever need to replace the mixer again will the compound actually come off?
     
  5. Lynn Dixon

    Lynn Dixon New Member


    Thanks for the reply
    1 - yes
    2 a yes but will try your suggestions too

    It will not beat me!
     
  6. I would just try ptfe tape over a new olive first. See if that sorts it before going further.
     
    Lynn Dixon likes this.
  7. Wayners

    Wayners Screwfix Select

    Buy olive remover. Hopefully you have enough pipe to try this. Remove olive. File off 2mm from pipe. Put new olive on. When tight the olive will sit in different spot so seal. Tiny bit of Vaseline on thread. Just a tad. Makes it easy to do up and judge how tight it is rather than get that stiff grinding. Nip up. No leak
     
    Lynn Dixon likes this.
  8. Lynn Dixon

    Lynn Dixon New Member

    Thanks all, will give the suggestions a try :)
     
  9. Pollowick

    Pollowick Screwfix Select

    Maybe try using a COPPER olive rather than brass. They are softer, easier to compress and mould to fit voids.
     
    Lynn Dixon likes this.
  10. Dr Bodgit

    Dr Bodgit Super Member

    LS-X is easy to apply and easy to get off too.
     
    Lynn Dixon likes this.
  11. Pollowick

    Pollowick Screwfix Select

  12. I wonder if there's a graze or mark on the fitting's mating surfaces that didn't quite seal?

    Anyhoo, Lynn, check that the copper pipe hasn't been crushed where the olive was sitting.

    Jointing compound is always a good idea when doing comp fittings. I use Fernox White, although that LS-X looks like more serious stuff.

    Get new olive as said before. Slip it well on, apply a smear of Fernox around the pipe (not inside...!) and pull the olive back over this bit until it's in roughly the right position. Then add another good smear over it.

    Apply more Fernox to the male fitting thread - this will reduce friction and make it all easier to do up.

    Fire away.
     
    Lynn Dixon likes this.
  13. KIAB

    KIAB Super Member

  14. No good for a compression fitting to wrap over an olive.
    This product is for use on the threads of male iron fittings.
    PTFE tape should not need to be used on compression fittings,I always assume a bit of a bodge when I see PTFE tape wrapped around a compression fitting.
     
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  15. Dr Bodgit

    Dr Bodgit Super Member

    I always assume a bit of a bodge when I see anything on a compression fitting. Application of LS-X for example implies it leaked without it.
     
  16. Pollowick

    Pollowick Screwfix Select

    Only time is if they are a bit tight/rough when screwing together, a wrap or two just acts as a lubricant.
     
    Deleted member 164349 likes this.
  17. Hmmmm, I think you'd be a bit nuts to not always apply a smear of Fernox White or similar to the mating surfaces AND the male thread on every comp fitting.

    You know it makes sense... :)
     
  18. Dr Bodgit

    Dr Bodgit Super Member

  19. andy48

    andy48 Screwfix Select

    For what its worth, my views on compression fittings and paste / tape:

    1. New Joints (new pipe and fitting). Small smear of Jetlube on olive faces of fitting and nut. Not really needed, but for the odd one which weeps at first, worth doing for all.
    2. Old joints (in good condition). Clean olive and mating faces of fitting and nut with "Scotchbrite" type abrasive, then as 1. above.
    3. Old joints (in poor condition). Prefer to remove old olive and replace with new then treat as 2. above. If not possible (e.g. olive overtightened and crushed pipe), 5 or 6 wraps of ordinary PTFE tape around olive after cleaning olive and mating surfaces of nut and fitting. .
    4. If in the mood, tiny dab of silicone grease on threads, but rarely in the mood. Silicone grease because I carry it. From memory Yorkshire Fittings recommend oil, presumably 3 in 1 type.
     
  20. kiaora

    kiaora Guest

    Hi
    In my view, apart from maybe a little ptfe or smear of boss white, if it leaks, it's the fitting got damage/crack, or it's not leaking.

    When I say it's not leaking ..... look again very closely

    Regards
    Peter
     

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