First - Terry and others on here are the best. I am in Houston, have gotten misinformation from many plumbers here and from vendors about my toilet installation, but the info I got on this site was life saver. Two contractors told me flat out they did not want the job. Three others failed my test question.
I have called and/or emailed Zurn, American Standard, Kohler,Geibert and TOTO and I have almost all the info I need to supervise this job. I have a Kohler residential wall hung unit (No longer offered) on an expensive floor to ceiling marble tile wall that previous owner put in so I do not want to disturb the wall the Kohler is on. The mounting is likely a Zurn back to back mounting. There is an old AS (Glenwall?) on the other side that I have to replace. I may have to adjust or replace the Zurn mounting because the house has settled and the mounting bolt connections are no longer level on the wall with the AS. I would also prefer to have ADA compliant height. I have been unhappy with the AS for 15 years and I want to replace it with a TOTO Aquia with Geibert in wall tank with back to back mount(got the spec sheets from Geibert). Since the Kohler unit is no longer sold I did not get what I consider to be reliable info from them.
My question is, can I put the Kohler and the Toto on the same back to back waste connection? One of the people I talked to said that Kohler is pressure assisted and TOTO is washdown so they cannot go on the same back to back conection because one requires verticle and the other horizontal. If true, I would consider replacing the Kohler as well. The AS toilet is in a nook, so aesthetically we can bring the wall out to accommodate the in-wall tanks, if needed.
Also, the one thing we do not know yet (have to take the AS off the wall to tell) is whether the waste pipe connecton is verticle or horizontal. Since there is a toilet directly above, we think the waste connection is into that same cast iron pipe, and probably horizontal. Would horizontal pipe nix the TOTO? If the best thing is to just put in a new Glenwall, I will hold my nose and do it.
I really appreciate your help.