Let me first say, I know I am tackling a big project and this is not a normal issue.

Here is a little of the scope:
I am remodeling my Second Bathroom on the 1st Floor. I am completely remodeling the entire room, new tub, shower fixtures, sink & faucet, toilet, tile, ceiling, drywall, electric, lighting, cabinets. The whole shot.
I have a Master Bathroom back to back with the above bathroom that I may remodel in 3-5 years
I have a bathroom in the basement directly under Second bathroom I am remodeling
I have a laundry room back to back with the basement bathroom that is unfinished and ceiling and pipes are exposed and accessible
Plumbing stack is cast iron and runs pretty much straight up and is drain for entire house. It has various vents in all the appropriate areas.

Here is the problem. I purchased a new toilet, and it is a wall mounted european toilet.
Okay, like I said above, I realize this is not the norm. I knew this was an issue, but am going to figure it out. This toilet is kind of crutial to the overall design of the bathroom.

Anyway, the toilet has a carriage system and tank that mounts in the wall. Of course, this is right where the stack is. Toilet also has a special elbow that you must use that drains straight down. The 2 toilets that are back to back are off a cast iron sanitary cross.

As far as I see it, I have a couple options:
1. Remove entire stack down easy working point (approx 48" above basement floor) and replace the entire stack with PVC (easier to work with) and then just reroute as necessary.
1a. If I take this route, should I just run new PVC vent through roof or tie back into cast iron vent that goes through roof. Worried about weight of cast iron vent. (Also, roof needs to be replaced and will probably be done next summer)
2. Remove stack above cross, drain new toilet into top of cross, use inlet of cross (old toilet inlet) as new vent point and install new PVC up and around. I am aware this will make a wet vent for the M.Bathroom toilet.
4. Reroute stack in cast iron.


Also note, given the supplied/necessary elbow fitting for toilet, earliest option for venting point is right below this elbow, which is below the floor.

Any help would be great. I fully realize this is a big project and anyone in there right mind would not do this, but I really want this toilet.

Thanks.
Matt

If this were my job I would go with door number one and start at the top and take out the old cast iron stack and replace with PVC. You must want that new toilet very badly to go to all, this hassle to install it. Good luck in whatever you decide. Tom

First off, I'm NOT a plumber, and I currently have ZERO experience working with cast iron (to be remedied this weekend)...


But. When looking around the 'net for help/advice regarding cast iron plumbing, the common thread was that old hubbed CI is a bear to work with, and that it's easier to replace it with PVC.

BUT.. PVC can be noisy. Ever been in a newer house, and literally "heard the turd" as it went past? Insulation supposedly helps, but not as much as just using cast iron.

Modern no-hub CI is supposed to be as easy or even easier to put together as PVC, though it is heavier by a lot (that's what keeps the noise down.. ) Bonus is that you can take it apart later, too. If it were me, and I were going all-out as you seem to be, I'd use a cast iron vertical stack, and use PVC for the horizontal runs and vents.

See this page for interesting reading: Plumbing Design

Scirocco's correct. Cast iron is quieter. I gave you the easiest material to install. And I have put in buildings using all three. However Sciroccos suggestion has merit. You could make the stack vent out of No-Hub cast iron and convert to PVC for the branches and to pick up the fixtures. It's a oiption and I like lots of options. Thanks Scirocco, Tom