: I have an old wall-mounted toilet tank that has a 2" line that runs to the back of the bowl section. This thing uses about 6+/- gallons per flush. It has a 15" rough-in (distance from wall to bolt holes). I want to put a 1.6 gallon (per flush) toilet in but most have a 12" rough-in. Other than the back of the tank being 3" from the wall are there any other ramifications that I need to be aware of if I go to the new system??

Dan,
Many toilets can be found with a 14" RI.
They are a little bit more, but don't waste that extra 2"
Other than that, it should work out.
Terry