Step 3 · Cut Out and Remove the Old Valve
With the valve exposed, you need to disconnect it from the house plumbing. You will see the hot and cold water supply lines connected to the bottom of the two outer valves, and two pipes coming from the central diverter valve: one going up to the shower head (shower riser) and one going down to the tub spout. Using a mini tubing cutter, cut the hot and cold copper pipes below the valve body. Then, cut the shower riser pipe above the valve body and the tub spout pipe below it. Once all four pipes are cut, the old valve assembly can be removed from the wall cavity. It may be screwed to a wood brace; if so, remove those screws.