I have a wc with the waste going straight down into the floor..I am remodeling the shower room so I need to remove the wc and replace..but I cannot see how the unit connects to the waste underneath. The rear of the wc is solid and therefore I am assuming that the unit push fits onto a waste that is protruding a certain amount from the floor and that by gentley twisting, I will be able to remove the wc bowl...am I correct or am I missing something??