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Thread: Venting a WC waste line horizontally

  1. #1

    Default Venting a WC waste line horizontally


    I'm planning on installing a WC and vanity in an upstairs loft. I plan on running a new 3" drain down through a 1st floor laundry closet and using an existing 3" vent in the attic for venting the new WC and vanity. The only thing on the 3" vent in the attic is a WC on the 1st floor. I think I'm ok on the number of DFU's for the existing 3" vent. My total will be 13 (2 WCs; 1 vanity.) I'm squared away on the vent for the vanity.

    I plan to attach the toilet flange to the finished flooring, and using ABS plastic, do a 90 degree turn out of the flange, go about 20" horizontally (with 1/4"/ft slope) beyond the finished wall into open attic space. From there the drain would do a 90 degree turn to the right and run horizontally through the sheet rock wall above the laundry closet about 3.5'. Then a 90 degree vertical turn down through the floor and tie into the existing main that runs out to the septic.

    The 2 questions i have are:

    1)-Can I vent off the 3" horizontal drain line in the attic area with wye while the drain is still running horizontal, or do I have to do the vent connection when the drain makes it's vertical drop. The vent part of the wye would be pointing up. It would make for a cleaner install to the vent connection in the attic area instead if inside the finished laundry area.

    2)-Is it ok to do a 90 degree turn out of the flange? There are 8" wooden I Beams as joist so I don't have alot of room for a more gentle bend (I plan on using a long 90 el there.) The joist run parallel to the 3" drain where it attaches to the flange and where I will punch through one, it will be above a supporting wall below.

    Thanks for your time. I live in California.
    Last edited by Jhall; 08-27-2009 at 02:05 PM. Reason: add location


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