Need to add second drain pipe to second floor?

EngineerChicMarch 25, 2012

We are mid-remodel. The house originally had 1 full bath on the 1st floor and 1 full bath on the 2nd. We are adding a second bath upstairs, and the 2 upstairs baths will share a wet wall ( the toilets are back to back against that wall).

The plumber says we may need to drop another drain line ... And I'm worried because I can't figure out WHERE that can be placed without tearing up the kitchen.

So, 2 questions...

1). Can 3 full baths share 1 cast iron drain (house was built in 1960's)?

2). If not, can a drain pipe run horizontally and cut through floor joists? I think that would require extra support for those floor joists somehow.

I do trust the GC but I'm also thinking that I want the best looking/functioning solution that minimizes the amount of demo to the first floor. And now I'm concerned about how that will be achieved.

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If you need another stack, put it in the same wall as the present stack if possible.

Running a 3 inch (let alone a 4 inch) line perpendicular to joists is a real PITA, and depending on the joist size may not even be possible.

    Bookmark   March 25, 2012 at 2:00PM
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Thanks, I thought the joists would be a problem. I think if we flip the fixtures (swapping tub/linen closet with toilet/vanity) I can get the new drain stack to drop through a closet on the first floor. I'll see what the GC and plumber say about it.

Anything to prevent a waste stack from becoming a stylish addition to the kitchen, right?

    Bookmark   March 25, 2012 at 8:42PM
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This question cannot be properly answered with the limited information available. Whether or not you need another stack is dependant upon how the bathroom on the first floor is vented.

    Bookmark   March 27, 2012 at 10:37AM
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