1. Loosen the 2 nuts that are located on each side of the toilet. Place them in a safe location, because you will need them to remount the toilet.2. Lift the toilet. Set it in a place where the rest of the water can drain from it, such as a shower or bathtub.3. Clean the wax from the flange seal, and then remove the screws that attach it to the floor.4. Measure the pipe that comes out of the floor so that you purchase the correct size. You will need to buy a new flange, a new section of pipe with the same diameter as the old pipe, a pipe coupling, a new wax ring and PVC glue if you do not have any.5. Cut off the flange at the red line. This can be done, from inside the pipe, using a Dremel tool with a reinforced disk for cutting.