Jog in vertical waste pipe

[DirtyBrad]

I have what I think is a simple question, but I'm coming up blank.

I'm redoing a first floor bathroom and moving one wall 9" so I can build a hallway. The stack that serves the bathroom is in that wall.

The second floor room above is currently open, so relocating the vent pipe up there is not an issue. There's also no problem drilling the new hole in the roof.

The issue is in the basement. The existing stack is 3" PVC and connects to 3" cast iron via a rubber donut. The cast iron runs vertically into the slab. Busting up the slab is not something I want to do, so I'm hoping I can offset the PVC and leave the cast iron where it is.

As I said, I haven't been able to find an answer to this. I'm in Montgomery County, MD, which uses the IRC, if anyone has anything specific to that.

I've included a diagram to help illustrate what I want to do. The jog I'm going for is below the lowest fixture this stack serves. The first floor bathroom is the only thing served by this stack.

Thanks in advance for taking a look.

 

[Terry]

Offsetting is not a problem. Go for it.

 

[Sponsor]

 

[DirtyBrad]

Fantastic, thank you very much. And thank you again for this forum. I've only posted a couple of times, but I read it all the time and it's saved me countless dollars and mistakes.

 

[Reach4]

I wonder if you might take the opportunity to add a cleanout while making changes.

 

[DirtyBrad]

There actually is one in the cast iron. There are two bells in the cast iron, the one pictured and another that I omitted that has a cleanout. I'm going to remove that cap, which is PVC, then plug that with rags to keep stuff from above falling into the pipe when I remove the upper bell and tie my PVC in. Would you recommend an additional cleanout in the PVC to keep things easier to work with?

I'm actually planning to put the new stack into a three way fitting, not an elbow as pictured; I was trying to keep my diagram simple. A major problem with the existing setup is that it's a waste/vent stack for the first and second floor bathrooms, including toilets. There are all kinds of venting troubles in the second floor bathroom.

I included a full diagram of my plan for the basement. The existing second floor bathroom (draining/venting in the middle of the three-way) has to stay until the first floor is functional. The first floor will run into the right side of the three-way. Once the first floor is finished, I'll cap the middle of the three-way and remove the current vent.

The left side will be capped for now, but will be available when I redo the second floor bathroom. When I do, I will run a second vent for it up through the roof or tie it to the existing vent in the attic.