Tools to Use:

Heat gun
Tongue-and-groove pliers
Hacksaw or PVC pipe cutter
Sandpaper
Gloves

Before you can remove the glue from the PVC pipe, you will have to separate the two pipes first. You can follow one of these methods:
Cut the PVC pipe.
Using your PVC pipe cutter or hacksaw, cut the pipe up to the section where you would like the pipes to separate.
Twist the pipe.
Twist the PVC pipes into opposite directions to provide sufficient torque and separate them from each other. For this process, you will need to use your tongue-and-groove pliers …