I am putting in a basement bathroom and do not want to mess with the old cast iron pipes any more than needs. We hammer drilled out trenches and then realized we could easily connect to a cast iron connection that was not deep. This has therefore left all the pipes 1/2 inch to 2 inches above the cement floor. We have used the small parts of the chipped-out cement to level the pipes and plan to fill with concrete to floor level. Is this okay to do?