I am installing a Vespin ll on a concrete basement floor .
My question is that my toilet flange is flush with the floor.
It is made of cast iron .
Can i install a unifit with jumbo ring with horn without any problems?
The instructions say to have the floor 1/4 inch above floor.
When I place a toilet adapter on the flange it doesn't sit right.
I understood the question up until the part where the Unifit adapter does not fit right. The flange not sitting proud of the floor is not going to be a problem. However I would like to understand the bit about the unifit not fitting right. I suspect you are saying that the floor is not level where feet of the Unifit touch. In that case, I would add a shim under the leg that sits high, and run the screw through that.
I think jumbo ring with horn sounds appropriate. When I put my Unifit in for my Vespin II, I formed the wax the way I wanted it with wax from two rings, wearing nitrile gloves. But as long as the wax gets squished top and bottom, you should be good with normal ring placement.
What is nice is that after you get the Unifit placed, you can set the toilet on. You can freely add shims around the toilet base without worrying about messing up the wax, as you would have to worry about with a conventional toilet. Rocking is easy to deal with.
Caulk around the base when the shims are placed. That is mandatory, because the caulk helps keep the front of the toilet in place.
If the toilet on the unifit is not going to sit where you would like -- for example you would like it a bit closer to the wall, say so. You can use the slack to slide the Unifit a bit. I did something more unusual to handle a case where my rough in was about 13 inches.