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New under slab drainage run

Discussion in 'Plumbing and Central Heating' started by MattChan, 2 Oct 2021.

  1. MattChan

    MattChan

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    Below is the floorplan of a small extension, its only the bit under the rooflight section that forms the extension and will have a slab poured over it.

    Green is the existing soil stack that feeds upstairs and vents through the roof.
    Purple is a new position
    Cyan is a new position
    Yellow is the ground box gas meter so the soil pipe can not exit here
    Red is existing pipe to sewer
    Orange is the proposed new inspection chamber

    Green is currently connected to red with a straight run followed by a 30deg bend.

    Can I have any bends or T's under the slab or do i need direct routes out to each position?

    [​IMG]
     
  2. Exedon

    Exedon

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    I would myself bring them out separately only short lengths involved put a new inspection chamber in the area marked in red.
    Have a look a building regulations H1 section 2.23 for advice.
     
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  4. MattChan

    MattChan

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    Point taken.

    I have read section 2.23. If I dont have enough cover I may need to reinforce the slab etc.

    I had a good read through and nothing seems to preclude the use of bends. For green ill need two 15 deg bends mid run, purple ill need a 30 deg at the output of the chamber and cyan ill need a 15 deg on the output of the rest bend.

    Am I likely to run into issues with the BCO taking this approach? Then don't seem to answer the phone or call back if you leave a message at the moment!
     
  5. Hugh Jaleak

    Hugh Jaleak

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    Bends are allowed immediately outside Inspection Chambers, I'd be very wary of putting them further along a run, especially under a slab. Junctions are permissible if the branch is pointing upward, e.g. in a run for a Cloakroom where the Hand Basin and WC are going into the same run, (like the letter F on its back), in the horizontal plane best avoided.

    You need to ensure all sections of the drainage system are accessible for rodding/jetting if need arises, rods and/or jet will not go round the corner if the branch run into a junction blocks, and you wouldn't want to be unblocking a WC from inside the house , believe me....

    I'd think you should be able to get all 3 runs out from the building into a 450mm chamber, use bends at the chamber to line things up.
     
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  7. MattChan

    MattChan

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    Well Ive got the IC in and some temp pipework in place. The pipe at the top of the picture is fixed in angle and position as its the existing stack outlet which is in the existing slab. The pipe at the bottom comes straight out of the new IC. The two bends are 15 degrees each.

    Do i need to chip out around the pipe / rest bend at the top of the pic so it can be moved for a straight run to the IC?

    [​IMG]
     
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