Step 4 · Clean and Prepare Pipe Stub-Out
After removing the valve, the old compression nut and a small brass ring called a ferrule will be left on the copper pipe. The nut will slide off, but the ferrule will be compressed tightly onto the pipe and must be removed. The best tool for this is a dedicated ferrule puller, which removes it without damaging the pipe. Alternatively, you can carefully cut a slot into it with a small hacksaw or Dremel (being extremely careful not to cut into the copper pipe) and then pry it off. Once the ferrule is removed, use a piece of emery cloth or fine-grit sandpaper to thoroughly clean the end of the copper pipe, removing any oxidation or debris until it is bright and smooth. Wipe it clean with a rag.