Flat Roof drainage run internally

Discussion in 'Builders' Talk' started by ChrisKay, May 15, 2019.

  1. ChrisKay

    ChrisKay New Member

    I have a flat roof which is enclosed on 4 sides, so I have to run drainage off it via the outlet down into and through the property before it exits and drains outside. The internally run pipework and junctions will all be boxed in and insulated, and I have building control ok for it, but what I need to know is what type of plastic pipe do I use to do the internal run? BC approved document H doesn't give much guidance, can it be the black rainwater pipework normally fitted outside to take rainwater from gutters, grey soil pipe or the red underground pipe? Guidance welcome
  2. dobbie

    dobbie Well-Known Member

    You will not be able to use the normal rainwater pipe because that cannot be sealed and is designed to just fit together and come apart for maintenance.

    You should probably go for 3" solvent weld soil/waste pipe with the appropriate rainwater flat roof outlet,depending on the area of the roof.
    The outlet would also need to be able to be cleared in case of blockage.
    Google terrain for more details on their systems.
  3. ChrisKay

    ChrisKay New Member

    Thanks, much appreciated
  4. Jimbo

    Jimbo Well-Known Member

    One question.., what happens if the soakaway gets blocked, in terms of the weight of the water accumulating on the roof.
  5. stevie22

    stevie22 Active Member

    It's not going to back right up to the extent that the roof ponds: water will well out of the soakaway long before that happens.

    It could easily back up a bit though hence the need for sealed joints
  6. CGN

    CGN Well-Known Member

    110mm soil pipe if space permits.

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