Hi Folks:

Thank you in advance for any help/advice you can give. :)

We knocked out a closet to enlarge our bathroom from 4'8"x9'6" to 7'2"x9'6". Our old plumbing (vanity, toilet & shower) were all arranged on the 9'6" north wall. Please see the top picture.

The drawing shows how we'd like to place everything and shows the existing floor drains. (There's also a sink drain on the left side of the 3" stack but I didn't know how to show it.)

I understand that the concrete slab is 6" thick. Can I cut out the slab where the existing toilet drain sits, take it out and run the new tub drain there? Also, can i cut out the existing shower drain and use that place for the new toilet drain?

Last: Can i use an air vent piping arrangement like the last picture instead of having a vent stack for the 30" vanity?

Thank you again for any help you care to offer. Sincerely yours, jim see

Attachment 4386

Attachment 4387

If you are will to cut AND replace the lines you can do pretty much everything you describe. You can't just put a toilet on the existing shower drain, you need to increase that drain to 3" or better yet 4". You could skip the vent stack for you sink by adding a Studor vent (AAV) designed to admit air drawn in by water draining. That DYI picture isn't too clear to me. It lookms like a big, worthless loop.

I think Bal made it sound too simple. Our code calls for 4" under the slab to pick up a toilet so the toilet and shower has to be jack hammered up and the drains resized and configured. Not knowing what way your sewer's running puts me at a disadvantage but it looks like you're gonna hafta run a 2" line from the 30" lavatory to the main and connect the tub drain to it for a wet vent. The bottom pic is a loop vent used to vent island sinks in the kitchen.
Sure looks like the long way to go just to avoid running a regular vent. And that's what I suggest you do. Run a vent on one lavatory and revent the other into it. I don't know how happy the inspector's going to be with loop or Studor vents venting a entire bathroom group. Call and ask before you install. Regards, Tom

Thanks for the help so far, Bal and Tom! The sewer runs to the street (from left to right in the picture). There's a vent stack in the middle of that wall.

Amy, my wonderful wife and the real boss now says that she'd prefer this setup
Attachment 4390

The small vanity, toilet and shower would use existing pipes and venting (through the cast iron stack). The new double vanity would require a new vent... I guess Would I still need to go under the slab for that drain? Or perhaps a better question is: What would be the best way to do this? There's no ready water access on this wall. In fact, there's no wall yet! :)

Thank you again! Sincerely, jim

You will have to break up the slab from the new lavatory to the main or the old tub drain line where you will cut in a wye or a combination wye and eighth bend to pick up the new lav. You will have to vent this fixture either by reventing bact to the original vent or, if code allows, by installing a AAV,(air admittance valve)
The other fixtures are good to go. Amy saved you a ton of labor by keeping the original configuration . Good luck, Tom