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Discuss Plastic pipe separating from compression joint in the Plumbing Forum area at

  1. dazroberts73

    dazroberts73 New Member


    I replaced our leaking bathroom tap yesterday, it’s one of these mono mixer types. The existing one had 2 copper connectors which then were connected to the plastic water pipes via plastic pushfit fittings. As the new tap had flexible connectors with a nut on the end I had to change the existing pushfit connections; I decided to use isolation valves, compression type.

    Fitting the tap went relatively smoothly, then on to the connection to the water pipe.

    The plastic pipe needed to be shortened to allow the connection, I used Rothenberger plastic pipe cutters (the handle type), the cuts were clean though not perfectly square; I used JG inserts for the end of the pipe, after sliding the nut and copper olive along the pipe.

    After tightening the nuts with the spanner I turned the water back on; to my horror, one of the connections blew completely off the pipe ! The other one was fine, not even a leak. After turning the water off and mopping up the bathroom I reconnected the pipe to the valve, ensuring that after hand tightening giving it a full turn with the spanner.

    This time I turned the water back on slowly, a quarter of a turn at a time – there were no problems, not even a small leak. I then checked to see if change in pressure would affect the joints by switching taps on and of, flushing the toilets and putting the washing m/c on. No more problems whatsoever...or so I thought.

    This morning, the wife put the washing m/c on, its one of these new eco friendly types that optimises water usage to suit the load by ‘pulsing’ the water in, so its more of an on-off, on-off, etc. Whilst it was doing this I heard a ‘pop’ upstairs followed by the gushing of water – the other connection had blown. So I followed the same procedure as per yesterday's conundrum, ensuring the joint was tightened a full turn with the spanner.

    Can anyone shed any light on why this might be happening? Its really concerned me the fact the 2nd one went 15hrs after it was fitted. I daren’t leave the house at the moment and am papping myself every time we use the washer.


  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Are you using the super seal inserts are these can't be used on compression joints ?
  3. dazroberts73

    dazroberts73 New Member

    Yes they are JG Speedift Superseal Tube Support. Why can these not be used? What should be used with compression joints?
  4. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    TSM PIPE INSERT | John Guest Speedfit

    The reason is the super seal have more of a shoulder so on compression not much of the pipe is in the fitting

    You could if you want to remove the big o ring on the super seal and cut / hacksaw the back face (if you understand what I'm saying)
  5. dazroberts73

    dazroberts73 New Member

    That makes sense now. I see the TSM has a chamfer to aid the install into the fitting. A lesson learned the hard way...
    Thanks ShaunCorbs
  6. SimonG

    SimonG Trusted Plumber Top Contributor!!

    I only carry superseal inserts. I just chop the head off once pushed into the pipe on compression joints.
  7. snowhead

    snowhead Well-Known Member

    As above correct sleeve type.
    Copper olive (compression ring)
    Tightend up enough.

    Lastly if in any doubt undo the joint and check that the olive has gripped into the plastic pipe.
    • Agree Agree x 1
  8. oz-plumber

    oz-plumber Plumber

    The problem with solenoid valves on washing machines is that when the slam shut, they increase the pressure in the piping 6 fold for an instant.

    So what ever fittings you are using, make sure they can handle a 600% increase in pressure for a second, umpteen times a day for umpteen years.
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