New Member with question about moving toilet drain

[user 32332]

Hey everyone, thank you for all that you do here. I work in the construction field (draftsman) so I am somewhat familiar with building materials, code, terminology but when it comes to plumbing vent flow, pipe architecture, I'm lost. My question is about relocating a toilet. In the picture below, you can see the existing toilet drain sloping down to the main drain stack which is vented up through the roof above where the other fixtures feed in. You can see where I have started the yellow line at the ceiling is where I need to relocate the toilet. My assumption is that I can run a new 3" drain line straight down and parallel the vertical drop of the main stack that is directly below it? Can I do this and feed it straight into a sanitary T at the existing line out to the septic and still use the same vent for this pipe? Thank you for your replies and for the hard work you plumbers put in on a daily basis, definitely a difficult job.

 

[MicEd69]

The short answer is no. And actually, you have some rather major issues with your current setup.

The current toilet is not properly vented, nor is the P-trap shown in your picture. It's hard to tell from the picture, but I'm assuming the P-trap is draining something directly above the P-trap. But it looks a little like the line going to that P-trap has a 90 above it and is coming from the right in the picture. If that is right, that is a big problem. Also, from the picture it looks like the P-trap is entering the drain line through a Sanitary tee on its side. If that is right, that too is a problem. I assume the line entering the soil stack from the right side of the picture is vented separately. If not, that would also not meet code.

Specifically, for your toilet relocation, you can do as you show if you add a vent at the 90 near the wall and run that vent vertically or no more than 45 degrees off vertical until it is at least 6" above the toilet bowl. Then you can run that vent horizontally at a 1/4" per foot slope as needed to get the vent above the roof or to attach it to the vent stack. With that being an exterior wall, you could possibly run that vent line out the wall, but there are restrictions on how that can be done.

You kinda have a mess there.