regardless of which is the case the right alngle piece that comes with the garbage disposal usually has a rubber o-ring seal that goes between the plastic or metal pipe flange and the disposal. also need make sure this piece of pipe is not canted up or down as it attaches to the drain piping. it needs to have no side or any kind of load applied or it might compromise the sealing surace back at the disposal end. good luck and hope this helps. LJ