There are many reasons why it might be necessary to remove an old toilet flange and replace it. If your toilet rocks or moves too much, then this could quite easily cause damage to the toilet flange, resulting in a replacement being required. It's also very easy to damage the flange if you are removing flooring or doing any decorating in your bathroom. A damaged toilet flange will result in leaks. Leaks from the toilet are highly unpleasant things in both smell and appearance.
Step 1 - Turning the Water Supply Off
First thing you need to do is switch the water supply off in your home. Either use the master shut off valve in the street, or alternatively you can use the shut off valve in line with the pipes leading to the toilet. This will ensure that the water won't continue trying to fill the toilet up.
Step 2 - Emptying Water
Empty the water out of the toilet by pressing the handle and flushing it. Because the water is turned off it won't fill up with any extra water.
Step 3 - Undoing the Toilet
The toilet is fixed to the ground using 2 nuts which are on each side of the toilet. Remove these nuts but keep them safe because they are required to reinstall the toilet later. If you really can't shift the bolts then they can be sawed off. They will need to be drilled later.
Step 4 - Removing the Toilet
Once the bolts have been removed, start rocking the toilet. The toilet is sealed against the flange using a wax seal so it might take some time before the toilet comes away. Once the toilet has been removed, you can then put it somewhere safe in the house. Putting it in the bath is one good idea. Alternatively, you can lay it on top of towels and put them on the carpet outside in the hall.
Step 5 - Cleaning the Flange
Clean away any remaining wax from around the flange and remove the screws which are fixing it to the floor. Keep the screws safe because you can reuse them later.
Step 6 - Removing the Flange
When removing the toilet flange, the methods used will vary depending on the type of material your flange is made from. You will either need to break the pipe by cutting into it using a dremel tool or by breaking the glue bond between the pipes. If the pipes are glued together then you should be able to use solvents to break the bond.
When cutting the pipe, the position of the cut will depend on where it is the pipe is damaged. Ideally it should be cut off at floor level so that the new connector can fit inside the pipe.
If using solvents, you must be careful because they could also eat away at the pipes. There are many different solvents that you can use, try to choose one which will work on the glue but not on the pipes themselves. An all purpose adhesive remover should be able to break the bond between the pipes without needing to worry about damaging the pipes themselves.