Leaking mdpe pipe at compression fitting

Discussion in 'Plumbing and Central Heating' started by sastek, 8 Jun 2021.

  1. sastek

    sastek

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    Hi, I need some advice about a leak. I recently had a leak from the underground stop cock for mains water, so replaced it with a new one. The problem I have now is that the mdpe pipe is quite loose at the compression tee, I can't get the nut to tight enough for the olive to clamp properly on the pipe. The pipe does have a insert, I've tried using a new olive and a used one that was in good condition. I'm wondering if it has something to do with the diameter of old black pipe vs new blue pipe.

    [​IMG]
     
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  3. muggles

    muggles

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    Almost certainly different diameters. I'd take the tee out and replace it with a Philmac one
     
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  4. CBW

    CBW

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    Iirc black pipe is 3/4”/21mm?
     
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  5. sastek

    sastek

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    The new blue pipe is 25mm, I'm wondering if the old black pipes are 1 inch
     
  6. polesapart

    polesapart

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  8. oph

    oph

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    Alkathene which is old hat from the 70s and mdpe on the right.

    Probably needs a transitional coupling to get from either material, not the tap.
     
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  9. JohnD

    JohnD

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    I have black alkathene incoming, and the main stopcock ( a brass one) is alkathene ?one inch? incoming and copper outgoing, quite a common size. I think your bit of blue pipe is the source of your trouble.
     
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  10. sastek

    sastek

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    Thanks for the responses, they were really helpful.

    So the new blue pipe is the wrong diameter, luckily I've found a bit of old black pipe to replace it with. I also think that the stopcock is the wrong size, it's for 25mm pipe. The manufacturer makes adaptors, so hopefully they work with this stopcock.
     
  11. JimCrow

    JimCrow

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    The stopcock you have ( Philmac 3G 2833) does both 3/4" Alkathene and 25mm MDPE pipe, no need for adaptors, use the original pipe you cut out with the olive from the brass compression tee to the stopcock.
     
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  12. sastek

    sastek

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    Well spotted Jim, thanks! For some reason I recalled it was a Plasson one.
     
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