Have an old toilet with a rubber adaptor system which steps up from 80 mm to 120 mm connecting to toilet bowl outlet. Is it true that new low flush units will not go through the 80 mm outlet in wall. Current high water usage system works well but ancient.

If this set up has worked on your existing system, then I'm pretty sure it will work with the newer systems, but I would strongly suggest that you call the manufacturer of the new toilet to be absolutely sure. Here, I can't see any company setting themselves up to lose business/sales, so I'm pretty sure they will have plenty of toilets that work just fine!

Mark

80mm is a bit larger than 3" pipe and this size is normal size pipe for toilet.

120mm is about 4 3/4" pipe. I have never seen toilet outlet this large - unless you measured O.D. of the bowl porcelain hub... However, you should be OK with the pipe you have.

Milo