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Thread: Soil Stack Horizontal Venting

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    Default Soil Stack Horizontal Venting

    I'm a Do-It-Yourselfer with a question. I'm remodeling my bathroom and want to install a small lavatory/utility cabinet in the wall behind and above the toilet tank. In doing so, I want to take advantage of the 3.5" stud cavity of the wall behind the toilet. As such, I will box-frame the rough opening of the cabinet space in the wall behind, and above, the toilet tank.

    My problem is that my main soil stack vent runs vertically right behind my toilet tank where I want to put my box-frame. (See attached .pdf pic.) Also, the main stack is cast iron for the first 35" above the floor. It then junctions with a with a no-hub fitting with PVC connection (all 4"" pipe) out through the roof.

    My question: Can I put in a 90 degree fitting to turn the main soil vent horizintally over two stud cavities (approx 24"-30"), run it vertically for about 3.5 feet, and then run a 90" turn to tie back into the original soil stack vent?

    The toilet tank is 29" above the floor so the 35" where my cast iron/no hub fitting ties in is 6" above the highest flood plane (the toilet tank). I've also read that you need venting to be 42" above the floor prior to horizontal runs. However, I thought that was applicable only to branch venting which ties into the main vent. If a 90" fitting won't work, could I run a 45 degree fitting (to fit drainage requriements) then go vertical and back with a 90 degree to tie into the main vent?

    Any comments would be appreciated.
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