Step 4 · Remove Old Nut and Ferrule
With the valve body removed, the old compression nut and the small brass ring, called a ferrule (or compression sleeve), will remain on the copper pipe. These must be removed. The ferrule is compressed onto the pipe and can be difficult to get off. The best tool for this is a compression sleeve puller, which neatly pulls the ferrule and nut off without damaging the pipe. Alternatively, you can carefully cut a slot in the ferrule with a small hacksaw or rotary tool, being extremely careful not to cut into the copper pipe itself, and then pry it open with a flathead screwdriver. Do not reuse the old nut or ferrule.