routing drain lines, IPC

[gilmil]

Hi There,

My wife and I are redoing our upstairs bathroom due to several mistakes made by the prior owners. The most major of which was cutting two floor joists in half in order to perform a plumbing repair:
!

Here's a horrible drawing of the bathroom layout and the plumbing the way that it was:


Pink = Fixtures, with the toilet being in the far corner
Blue = joists
Red = existing drain lines
Green = cut joists

So the 5 million dollar question is how does one get the drain pipe from the tub end of the bathroom to the toilet drain?

Thanks so much,
Gil
Sistering joists in steamy CT

[gilmil]

After reading some posts I'm going to work on a 3D diagram of this and post it sometime soon.

[jastori]

edit: Ooops... I think I misread... if you need to pass a 3" drain line through the joists, it is significantly more difficult, but may be still possible. It is certainly preferable to avoid having a 3" or 4" drain pass through joists.

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You should be able to drill holes for the tub drain to pass through the floor joists without causing structural problems. The common code requirement for drilling holes is to stay 2" away from top and bottom of joist, with max. hole diameter less than 1/3rd joist height (note: notching guidelines are significantly more restrictive). For a 2x10 or 2x12 floor joist, you should be able to safely drill for a 1.5" or 2" drain line to run the tub drain line through the joists.

The link below has code requirements for notching and drilling studs. I think their diagram is consistent with 2003 IRC.
http://www.ci.bloomington.mn.us/hand...3/53znotch.pdf

[jadnashua]

There is a potentially significant additional criteria about when and where you can drill holes in the joists...they can't be within x of the ends of the span (don't remember the x). In the middle of the span, the majority of the strength in stiffness is from the top expanding, and the bottom compressing, but at the wall edges, you need to account for the point loads of the walls, so holes there are more of a problem (and for probably other reasons, I've forgotten!).

[hj]

My first requirement would be to physically see the house and the installation. There are things not shown in the picture or the drawing which might impact how to do it, such as which end has the tub drain, and why? One indication that it was NOT a plumber who did it is the use of a bushing to connect the drain to the closet bend fitting.

[gilmil]

The layout was the original to the house, or at least was galvanized drain pipe and some brass water pipes. The drain for the tub is at that end because there is a window on the other end of the tub. We decided to keep the layout the same, but it was brought up to code.