31+ Floor Mounted Rear Outlet Toilet Background . The second is an old, 1970s kohler with a huge, 3 gallon tank, located in a very small. In many cases, your residential plumbing system and pipes are already fitted and ready to go, and quite often they are built for floor mounted models as opposed to back flow toilets. Sydney Smart Back Outlet Toilet Caroma Usa from www.sustainablesolutions.com You won't overpay for 1.1/1.6 gpf, flush valve, floor mount, elongated, toilet bowl, white and 1.2 gpf, gravity fed, floor mount, round, tank toilet, white when you shop with us. Or i could run the 1 1/4 pipe to the right to connect to the existing sink drain pipe. Which provides stability and a heavier flush without using up too much water. Rear outlet toilets are rarer in residential areas, but not uncommon. I have all of the walls up except for the ones where the toilet plumbing is goin...