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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book.

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    • CommentAuthorCerisy
    • CommentTimeDec 8th 2014
    Starting to sort out the drainage inside our new build and I'm stumbling over the wall hung toilets. We'll use Geberit Duofix frames, but as the family bathroom and the en-suite are next to each other, the toilets are close to being back to back. The drainpipe sits between the metal web joists and one of the toilets will sit over the top, so an easy connection - it's getting the other into the pipe at around the same place.

    The back to back bit sounds sensible, except I can't picture how the wastes can enter the main drain run at the same point. I'm clearly missing something - has anyone done a back to back installation?

    Thanks Jonathan
    Each toilet should have its own drain exit, even if they are close together

    Are you trying to run both toilets into one drain exit? Difficult for me to picture what you are describing.
    • CommentAuthorCerisy
    • CommentTimeDec 8th 2014
    Just as hard for me to picture it too!! These wonderful metal web floor joists that allow easy access for the electrics, etc, are really an obstacle when it comes to anything larger like a 100mm drainpipe. No, I don't think I need to fit them into drain exit - that would be weird - but with one sitting over the top of the best place for the drain run for the remaining fittings and the other 255 away from the pipe I can't visualise what fitting I can use to give a decent access into the main run.

    I will have to try alternative run positions - maybe a short vertical for the toilet over the top of the pipe to go in sideways and an air-admittance valve on top. The main run can then take the other fittings and continue to the vent in the roof. Now ideal ... but!!
    • CommentAuthorCerisy
    • CommentTimeDec 8th 2014
    Doh - alternative run positions may work. I'll take the toilet exit sitting on top of the pipe sideways, away from the flow, and then onto the pipe with a normal connection. The initially direction of the flow shouldn't be a problem as it's all downhill (so to speak!). This then clears the way for the other toilet waste to exit down through the floor, turn 90 degrees onto the pipe, with the connection being under the other toilet!! They are separated so that's good and the drainpipe continues and picks up the two basins, the shower and the bath - so there is still loads of water to keep it clean!! It then turns up into the roof space and vents, so that's covered. Now to work out all the fittings using what's available over here!
    While not a reglementation, It is considered good practice in France to have one evacuation pipe for black water and one for grey water. Just to give you even more of a headache!

    Only rainwater pipe and black water pipe need to be kept separate by law.
    • CommentAuthorCerisy
    • CommentTimeDec 8th 2014
    Nice challenge - but after struggling all day trying to picture this (both on paper and on site!) I may just pass!! Plus I like the idea of using the grey water to keep the everything flowing! As it all goes to the fosse and then into the ground we're keeping it all in the loop - so to speak!!

    I also have to find a path for the second vent from the front end of the fosse up into the roof space (also 100mm) and then thread the MVHR ductwork through it all!! Hey Ho!
    I have metal web ceiling joists and back to back toilets in the bathroom and en-suite. This is the arrangement I have and the BCO has okayed it, but it is in England.
    and upstairs.
    • CommentAuthorCerisy
    • CommentTimeDec 8th 2014
    Like it - I guess I've just got to see what's available in the plumber's merchants and work with that! Great photos thanks!
    • CommentAuthorCerisy
    • CommentTimeDec 8th 2014
    Just been pondering on how to get all these pipes to pass by each other and it dawned on me that we could have a problem here!

    The main drainpipe is open at the top as the vent pipe to the system, so could be drawing cold air down. Although it does go into the nice and warm fosse septic! The second pipe also goes to the open air through the roof vent and connects to the front end of the fosse, preventing any issues with pressure differentials - but that is likely to be a big cold spot in the house. Decent insulation is required - more work!!
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