Step 4 · Remove the Old Angle Stop
This step requires two wrenches to prevent damage. Place one wrench (or channel-lock pliers) on the body of the angle stop to hold it stationary. Place your second adjustable wrench on the large compression nut that connects the valve to the copper pipe coming out of the wall. Turn this nut counter-clockwise to loosen it. This may require significant force if it's old. Once loose, unscrew it by hand and slide the entire old valve off the pipe. Next, you must remove the old compression nut and the brass compression ring (ferrule). The ferrule can be stubborn. You can try to gently pry it off with a flathead screwdriver, but be careful not to scratch the pipe. A dedicated ferrule puller tool makes this much easier and safer.