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Discuss Compression fittings. How tight? in the Plumbing Forum area at UKPlumbersForums.co.uk.

  1. jrtrrror

    jrtrrror Member

    Hi all
    I have just finished the last thing in our ensuite. The thing I was most worried about actually.
    I had to re-install the shower valve onto my new pipework.
    Anyway, after installation I had a few little drops of water from one of the compression nuts. I nipped up the nut a little more and it's almost stopped. I'm very worried about applying too much force to the compression and making it worse.
    How tight should these compression fittings be .I've read lots of posts all saying different things. I.e. hand tight and then ¼ turn, or ½ turn or even 1 turn. One whole turn compared to ¼ is fastly different. And when people say 1 turn, do they mean one whole revolution, 360°.
    I'm only using a small compression fitting spanner that I bought from Screwfix, so not massive.
    I didn't apply PTFE tape or any jointing compound either.
    What's your advice? I believe there is still some turning left in the nut, but like I said, I'm scared of making it worse. I don't want to deform the pipes, that would be a nightmare to sort. Removing all my new tiles etc.
    Thanks
     
  2. Chuck

    Chuck Well-Known Member

    Buy a decent quality brand, such as Prestex, my favourite, and read the data sheet, e.g.

    https://www.pegleryorkshire.co.uk/M...13_Prestex_Compression_Plumbing_Solutions.pdf

    and follow the "How to make a joint instructions" it contains.

    For this brand it's 3/4 to 1 turn from finger-tight. "Jointing compounds or sealants are not necessary with PRESTEX fittings; the use of these materials could impair the efficiency of the joint and may contravene local water regulations."

    1 turn = 360°.

    In my opinion, only use compression fittings where you can't use soldered (capillary) joints for some reason and don't bury them in places where they could leak without being seen.
     
    Last edited: Dec 10, 2018
  3. gmartine

    gmartine GSR

    Use a bit of jointing compound like Boss white
     
    • Agree Agree x 2
  4. jrtrrror

    jrtrrror Member

    Hi. Thanks for your replies. Any interest people take is appreciated l, even more so when they contribute. However, the compression fitting in question is the inlet valves on the shower valve, so it's not a case of buying a quality product, I have to use this shower valve.
    So, just to clarify the walls are all tiled up and my pipes were sticking out of the tiled walls. All I had to do was install the valve. I'm pretty sure that I haven't turned the nuts anything like ¾ round. They are quite tight, but I could turn them quite a bit more I guess, even with the small compression spanner I'm using. I just didn't want to make it worse. I will only get one chance at this. If I wreck the pipe, I'll have to remove tiles and plasterboard in order to install new pipes.
    Sorry, I have taken a picture of the valve in situ. I can do later, if needed. But it just a valve fastened to the wall, with two inlets.
    Ta

    Screenshot_20181210-061957.png
     
  5. Ben-gee

    Ben-gee Plumber Top Contributor!!

    Carry on, that thing will dig into to palms and really hurt long before you over tighten the fitting.
    I too would wipe a little ‘jet lube’/boss white onto the olive before tightening.
    So; remove valve, wipe on compound(tiny smear), refit valve, tighten compression nuts.
     
  6. WC1

    WC1 Active Member

    Anyone ever use a tiny dab of LSX on tricky compression fittings when you're in a spot?
     
    • Like Like x 1
  7. Ben-gee

    Ben-gee Plumber Top Contributor!!

    No, if it comes to that - olive puller and start again.
     
  8. jrtrrror

    jrtrrror Member

    Thanks. Out of curiosity, and because I can't be bothered to investigate right now(too busy) how does boss white work?
    Thanks again
     
  9. WC1

    WC1 Active Member

    Water only needs an absoulutely microscopic gap to get through and cause a "weep" ! these joint sealing compouds seal all of those tiny invisible gaps that metal surfaces have. Check youtube of more, but well done for doing some research.
     
    • Like Like x 1
  10. Chuck

    Chuck Well-Known Member

    It's an inert viscous paste intended for use as a thread lubricant/sealant and not suitable for potable water systems. If you read the manufacturer's catalogue:

    https://assets.ctfassets.net/wt7f3t...403801fe935909223201b2e5c04/8805675728926.pdf

    This does not list applying it to the olive of a compression fitting as an intended use and I've never found it necessary. (I only use good quality brassware, however, no rubbish bought in bulk from China via Ebay.)

    It's proper use is on systems where the thread forms the sealing surface.
     
    • Agree Agree x 2
    • Like Like x 1
  11. Wirdy

    Wirdy Member

    On re-used compression fittings or new fittings onto old pipe I use a light smear of LSX (or the cheaper stuff from screwfix). Shouldn't ever be needed for new fittings onto new pipe, if done properly.
     
    • Agree Agree x 1
  12. Ben-gee

    Ben-gee Plumber Top Contributor!!

    Jet lube is suitable, can’t remember who makes it
     
  13. Wirdy

    Wirdy Member

    It's made by jetlube! ;). Fine for potable too. Good stuff, & it's mil-spec too iirc.
     
  14. Pickwickpick

    Pickwickpick Plumber

    What's mil-spec?
     
  15. Wirdy

    Wirdy Member

    To military specification. Has undergone & passed much stricter tests than run-of-the-mill products.
     
    • Like Like x 1
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