How to connect metal coupling to plastic pipe?

Posted on February 28th, 2010 by admin in metal | 7 Comments »

I have a leak on the inlet to my toilet cistern. I have bought a replacement metal coupling which I connected ok to the mains plastic pipe, but when I connect to the plastic threaded pipe attached to the inlet valve it leaks. What should I usse to prevent the leakage?

PTFE Tape. Like this:

http://www.plumbworld.co.uk/ptfe-tape-171-0000
http://www.diy.com/diy/jsp/bq/nav/nav.jsp?action=detail&fh_secondid=9265394&fh_location=%2f%2fcatalog01%2fen_GB&fh_search=ptfe&fh_eds=%c3%9f&fh_refview=search&ts=1199488473747&isSearch=true

Wrap it around the thread and then screw it in. Try to get it going the right way (with the thread) so that when you screw it on the tape does not unwind.

7 Responses

  1. SteveLaw Says:

    PTFE Tape. Like this:

    http://www.plumbworld.co.uk/ptfe-tape-171-0000
    http://www.diy.com/diy/jsp/bq/nav/nav.jsp?action=detail&fh_secondid=9265394&fh_location=%2f%2fcatalog01%2fen_GB&fh_search=ptfe&fh_eds=%c3%9f&fh_refview=search&ts=1199488473747&isSearch=true

    Wrap it around the thread and then screw it in. Try to get it going the right way (with the thread) so that when you screw it on the tape does not unwind.
    References :

  2. xenon Says:

    TIP from ex-plumber retired, It’s very common to get a leak from these fittings as it is not possible to increase the torque on a 1/2" plastic male stub.
    Buy a "Speedfit" fitting !/2" Femaleon one end and push-fit 15mm on the other end.
    Wrap the male stub in ptfe tape and tighten the fitting HAND-TIGHT, push in the plastic or metal pipe WAR OVER
    This special fitting works because the rubber washer is integrally factory fitted, and retained in a flange., the depth of the body is greater than a metal type giving greater strength.
    When I was plumbing, I nearly broke down in tears with an installation that was at a higher pressure than normal, I fitted a Speedfit, and never looked back, as I continued using them until I retired. I am surprised that the manufacturers of cisterns don’t suggest them for ALL installations.
    References :

  3. Brenda Says:

    plumbers tape (white)
    References :

  4. jay p Says:

    tee paste. it is safe on plastic and holds up better than teflon tape and its easy to use. dont overtighten the connection and strip the plastic threads.
    References :

  5. stitched up Says:

    You may find you have cross threaded it, take it off and check that it is square.
    References :
    Plumber

  6. nosdda Says:

    Try PTFE tape, but never overtighten on a plastic thread. You can also use jointing paste available from plumbers merchants.
    References :
    Plumber.

  7. gerzenplerter Says:

    Your plastic thread on the inlet valve could be split.. So no amount of washers or sealant will work. You might end up having to replacing the inlet valve completely.
    References :
    Plumber with 30 years experiance.

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