Step 4 · Clean Pipe and Remove Old Ferrule
With the old valve removed, you will see the old compression nut and a small brass ring, the ferrule, still on the copper pipe. Slide the old nut off. The ferrule is often compressed tightly and can be difficult to remove. The best tool for this is a ferrule puller, which safely pulls it off without damaging the pipe. If you don't have one, you can try to carefully cut a slot in the ferrule using a mini-hacksaw or a Dremel tool with a cutting wheel. Be extremely careful not to cut into or score the soft copper pipe underneath. Once you've cut almost all the way through, you can use a flat-head screwdriver to pry it open and pop it off. After the old ferrule is removed, use a piece of emery cloth or fine-grit sandpaper to thoroughly clean the last inch of the copper pipe. It should be smooth, shiny, and free of any burrs or old sealant.