Step 4 · Remove Old Compression Ring and Nut
After removing the valve, the old compression nut and the small brass ring (called a ferrule or compression sleeve) will remain on the pipe. Slide the old nut off. The ferrule is often stuck fast. The best way to remove it is with a dedicated 'compression sleeve puller' tool, which pulls it off without harming the pipe. Alternatively, you can very carefully cut a slot into the ferrule with a small hacksaw or a mini tubing cutter, being extremely careful not to cut into or score the copper pipe itself. Once slotted, you can pry it open with a flathead screwdriver and remove it.