Does a flange exist that allows a toilet on the second level to drain into the same pipe as one on the first level of a house. A Y type of fitting I suppose. Issue is plumbing is in the concrete and where we want the upstairs toilet is basically right above a downstairs toilet. If they could both drain to the same sewer pipe it would be terrific.

Does a flange exist that allows a toilet on the second level to drain into the same pipe as one on the first level of a house. A Y type of fitting i suppose. Issue is plumbing is in the concrete and where we want the upstairs toilet is basically right above a downstairs toilet. If they could both drain to the same sewer pipe it would be terrific.
I'm assuming the downstairs toilet's vented back into the same stack that you wish to discharge the upstairs bath room group into.
You may do that only if you disconnect the downstairs vent and run a separate vent up to the attic where it can revent back iinto a existing roof vent. Once you connect the upstairs bathroom group to a vent stack it ceases to be a vent stack and becomes a stack vent. If you go this way the downstairs group will have to be vented separately. Good luck, Tom

Thanks for your response. We have two other points at which we can vent the system, so I don't think that is necessarily a problem. The question is, is there a fitting that will allow me to seat one toilet and drain another into the same pipe? The fitting is what I am having a difficult time finding! wwerickson

Sorry you didn't get the information you asked for. I probably deserved the bad mark you gave me. Let me answeer your question now. A double sanitary tee, (see image) or a double combination wye and eighth bend,(see image) will do the trick. Your choice. Regards, tom