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Discuss What size is my copper pipe? in the Plumbing Forum area at

  1. MeWxm

    MeWxm New Member

    Okay, I know what size it is. It seems to be 15.5mm OD. 0.5mm of crud doesn't seem likely, so what size pipe could this be. I've measured some actual 15mm pipe and that is pretty much 15mm, plus a couple of thou. From what I've read, 1/2" UK copper pipe would be slightly smaller, not larger, than the 15mm pipe.

    What could ours be, and where could I get compression fittings for it?

  2. quality

    quality Plumber GSR

    there is only a few thou difference in metric 15mm compared to old 1/2" so i would worry . 22mm and older 3/4" do differ but 28mm and 1 1/8 are also only a few thou different
  3. Last Plumber

    Last Plumber Plumber GSR Top Contributor!!

    Old 1/2" is normally a bit tight in 15mm fittings so it will be that I would expect.
    • Agree Agree x 3
  4. MeWxm

    MeWxm New Member

    Thanks quality... are you saying I should worry, or do you mean I shouldn't worry? I don't want to cut into the pipe unless I'm sure what it is as that means no water in the house..
  5. MeWxm

    MeWxm New Member

    Thanks Last Plumber. Can you get 1/2" fittings or only the 15mm ones these days? I'd read that the 1/2" was smaller OD than the 15mm; not sure where though.
  6. Best

    Best Trusted Plumber Top Contributor!!

    The 1/2" is definitely slightly bigger than 15mm.
    I think you still can get solder changeover connectors for it.
    A 15mm compression fitting usually will be wide enough to fit 1/2", although these cheap brass fittings nowadays are often too tight on the 15mm and the brass nuts are too tight.
    • Agree Agree x 1
  7. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Might need to file / sand the pipe a smudge but should fit
  8. richard978

    richard978 Member

    I don't think you'll have a problem with 15mm, its 22mm where the issues are and most plumbers merchants sell fittings for this.

    I can't remember ever having a problem with 15mm copper or imperial 1/2 its close enough to use modern fittings.
  9. Ric2013

    Ric2013 Plumber Top Contributor!!

    BES sells imperial endfeed adapters, but most merchants don't. Apparently most people just sand it down a bit if it's tight!
  10. richard978

    richard978 Member

    A sad day when merchants don't sell imperial adaptors, every reason not to use the large chains and stick to local independents....who will always sell them. We have Bilbecks and Cooper & Berrys....they sell everything.
    • Agree Agree x 1
  11. Last Plumber

    Last Plumber Plumber GSR Top Contributor!!

    A 15mm will normally tap on. Maybe use a bit of emery paper if it's too tight. Or as Best said, compression.
  12. Stigster

    Stigster Plumber

    The answers here are all good and correct but if you are still nervous about not getting a fitting on you could always keep a quality pushfit fitting to hand which will fit the pipe for sure and then you would have an alternative if the job turns into a nightmare. I think you will be fine using the suggestions in this thread though.
  13. tolly

    tolly Plumber GSR

    Cutting the pipe with a pipe slice as opposed to a hacksaw will help you get the fitting on if its imperial 1/2"
  14. peter0504030201

    peter0504030201 New Member

    i would get a few 15mm x 16mm brass compression fittings just in case, you can get them from most city plumbing merchants , if not hit a 15mm pushfit fitting on with hammer if you have a nightmare as suggested :)
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