I am removing a downstairs loo (it is being relocated). How should I go about capping off the waste pipe that is in the floor? The existing toilet seems to have a ceramic down pipe which has been cemented into this waste pipe. The diameter is much wider than a normal waste pipe, hence why the toilet appears to have been cemented in place. My first thought is to just in fill the hole with concrete, since the pipe is only used by the loo. I just wonder if this would provide sufficient insulation from gases in the pipe?