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maximum length of horizontal soil pipe run

Discussion in 'Plumbing and Central Heating' started by rob7475, 27 Jan 2017.

  1. rob7475

    rob7475

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    Hi,

    I'm renovating a back to back terrace and want to move the bathroom to create an extra bedroom.

    This means the new bathroom will be at the back of the house. I plan to run the soil pipe from the back of the house (about 4.5 metre) between the joists, out of the front, 90 degree bend then about 2 metres to the current vertical soil stack.

    My measurements are only approx at the minute but the total run from the toilet to the vertical stack may be around 6.5 metres - will it be a problem if I go over the 6m limit. Could I fit an AAV internally to overcome the issue?

    I also plan to connect the sink and bath waste into the soil pipe. Should I make this connection under the floor or extend the soil pipe closer to the bath, then connect above floor level and box in?

    Thanks
     
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  3. muggles

    muggles

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    An AAV would certainly help. Make sure you get a good consistent fall. Recommended fall is 44mm per metre, so I hope you've got very deep joists if you're planning a 4.5m run between them, as that's a 198mm fall on a soil pipe which, with fittings, is about 140mm diameter, ergo you need joists 338mm deep to achieve your plan
     
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  4. rob7475

    rob7475

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    I thought the minimum fall was 18mm per metre? I was going to aim for 20-25mm.

    My other option is to run the pipe internally but would require a few bends - is there a limit to the number of bends you can have on a soil pipe?

    Third option is saniflo - not sure if these are any good or not?
     
  5. muggles

    muggles

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    Minimum is 18mm per metre, recommended for best performance is 44mm, and as you're going for a run which is longer than the maximum I wouldn't advise going anywhere near minimum fall. Two wrongs don't make a right!

    There's no fixed limit on the number of bends that I'm aware of but each one will produce a restriction and increase the chances of blockage

    Saniflos are the work of the Devil
     
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  7. rob7475

    rob7475

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    OK. at a push, I can lower the ceiling of the living room below to get a decent fall. It's a high room so dropping it won't be a big issue if needed.

    My main concern is the 6 metre rule as I'm going to have to get the council in to sign it off. Does the addition of an AAV near the toilet end increase the 6 metre limit?
     
  8. rob7475

    rob7475

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    Anyone?
     
  9. Agile

    Agile

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    Does anyone know where this 6 m rule is written down?

    Outdoors drains can run a very long way!
     
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  10. jeff the gasman

    jeff the gasman

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    When I was an apprentice it was always a minimum of 1 inch in 10foot.
    They use little inches nowadays
     
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    DIYnot Local

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