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Discuss Bath P-trap Inlet Lower than Outlet in the Fittings & Pipes area at

  1. Billy Whizz

    Billy Whizz New Member

    Hi all,

    Just fitted a new bath (height fixed due to bath panel). Plughole mechanism now means the bath waste connection is an inch lower than the original and hence there is no fall on the wastepipe. Soil pipe connection cannot be lowered to compensate.

    How can I raise the P-trap outlet higher than the waste inlet to reproduce the fall on the waste pipe again?

    Many thanks & best regards,


  2. PAUL JA

    PAUL JA New Member

  3. Billy Whizz

    Billy Whizz New Member

    Thanks Paul JA. A little too long unfortunately. :-(
  4. JCplumb

    JCplumb Plumber

    How long is the level run of pipe?
    If it's only a foot or two you should be OK, I've seen much worse perform well, much longer than a couple of feet and you will need to adjust it. If the fitting posted above fits then that will do fine as long as it doesn't increase the water level in the trap too much. If it does raise the water level too much, you could use an adjustable trap to get the level right. You only need approx 1cm per meter drop on the pipe.
  5. Best

    Best Trusted Plumber Top Contributor!!

    Is the waste pipe level and how far does it travel at level (or wrong fall) ?
  6. JCplumb

    JCplumb Plumber

  7. Best

    Best Trusted Plumber Top Contributor!!

    Adjustable trap will probably not be any use as it only normally allows trap to lower, but not go higher than standard traps. But some do vary.
    • Agree Agree x 1
  8. JCplumb

    JCplumb Plumber

    In conjunction with the item linked in the first reply.
  9. oz-plumber

    oz-plumber Plumber

    Might be a case of making a trap out of solvent welded fittings.
    We do this on occasions when in a similar situation.
  10. PAUL JA

    PAUL JA New Member

  11. Stigster

    Stigster Plumber

    • Like Like x 1
  12. Billy Whizz

    Billy Whizz New Member


    The pipe run is 1.2m and is currently falling 3cm towards the bath (the wrong way). If I can raise the outlet until the pipe run touches the first bath support rail (adjacent to the trap in the first image) it will at least bring it level.

    Will have a go at some of the shorter McAlpine couplings.


    I had considered the welded fittings but would rather something that can be unscrewed if needed.


    Tried one of those. Looked good but not enough clearance due to adjacent floor-level bath support.

    Thanks for your input guys, plenty of food for thought..

    Best regards,

  13. JCplumb

    JCplumb Plumber

    With an adjustable trap and the extension piece in the right place you can control the height of the trap exit to get the waste pipe exactly where you need it.
    Here's a hi-def photo of one I did earlier. I used the same camera I used to photograph my wedding so the quality is awesome.
    The arrow on the left is where you adjust the trap which will raise lower everything else to where you want it.
    The pink bit is the extender that Paul JA linked on the second post.
    The waste pipe is green because it's now in the right place :D
    amazing diagram.png
    But the McAlpine trap that Stigster linked above may also work ;)
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