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Discuss Bathroom waste pipes in the Bathrooms, Showers and Wetrooms area at

  1. Hoof Hearted

    Hoof Hearted Member

    I want to convert an unused bedroom into a second bathroom. It's convenient because the soil pipe is right outside this room. It's a large room. so I want to have a toilet, bidet, sink, bath and shower cubicle.

    The first plumber who I spoke to emphasised the need to have a separate waste pipe for the shower, in order to prevent water backing up from the sink or bath in the event of a blockage. I spoke to another plumber yesterday who said a single waste pipe will be fine so long as it is 2 inches.

    Who is correct? and are there any regulations on this?
  2. Riley

    Riley Plumber GSR

    2 inch better also remember a new bathroom is notifiable
  3. Hoof Hearted

    Hoof Hearted Member

    Thanks for the reply. Do you mean a 2 inch single pipe is better?
  4. Riley

    Riley Plumber GSR

    Depends on your space available but 2 inch will suffice.
  5. Hoof Hearted

    Hoof Hearted Member

    Plenty of space available and the joists are running the correct way towards the wall where the soil pipe is. I just want to be sure that a single waste pipe is sufficient. My next door neighbour has two 32mm waste pipes exiting the bathroom into the soil pipe. One for the sink and one for the shower.
  6. Riley

    Riley Plumber GSR

    Shower should be minimum 40mm. As said it’s enturely up to you. In my view 2 inch will suffice. If you want to eliminate any risk of backing up then run two pipes
    • Like Like x 2
    • Agree Agree x 2
  7. YorkshireDave

    YorkshireDave Plumber

    2" is cheaper, but personally I'd do them separately and ALWAYS is properly supported solvent weld with access tees for clearing out.
    Plan for the worst and it never happens. Hope for the best and be bitterly disappointed...
    • Like Like x 1
  8. king of pipes

    king of pipes Trusted Plumber GSR

    Run them separately is the best way cheers kop
    • Agree Agree x 2
  9. hammers4spanner

    hammers4spanner Plumber GSR

    Bedroom to bathroom hmmm joist issue here with the extra weight.
    Building control may want to nose on this
    • Agree Agree x 1
  10. Riley

    Riley Plumber GSR

    DID say it’ll need notification
  11. Stigster

    Stigster Plumber

    As KoP says, two pipe runs is better. I would only combine them if there was no other alternative for a separate shower waste run. If you've got the space and route, always go for a separate pipe. There's nothing really to be gained by running a shared pipe other than if space is a real problem.
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