Turn off the water to the house. Open the shower valve to relieve the water pressure in the lines. Disconnect the faucet handle and the escutcheon plate by removing the screws.
Remove the old assembly from the front wall, if the opening is large enough. Cut an access hole in the back wall to remove the old component, if a large opening is required. Cut the drywall with a utility knife. This makes the repair of a drywall hole easier than replacing the tile.
Unscrew the shower pipe and the pipe for the tub spout out of the old valve. Disconnect the hot and cold water lines. Cut the water lines or apply heat to sweated pipes with a torch.
Follow the manufacturer’s instructions for preparing the cartridge. Turn the cartridge so that the marking "hot side" appears on the left had side of it. Perform other checks as instructed.
Install the straight copper pipe into each adapter. The adapters screw into the valve. The pipe drops down from the adapter. A copper repair coupling that secures a short length of pipe to the cut water supply riser.
Clean the copper repair coupling with the wire solder brush. Apply solder flux over the edge of the pipe screwed into the adapter and on the cut pipe. Place the repair coupling over the edge of the adapter pipe. Insert the end of the cut water line into the other end of the coupling. Heat the pipe with a torch and solder the coupling into the new valve.
Connect the shower arm to the top outlet. The top outlet is the elbow connected to the end of the pipe. Apply pipe wrap to the end of the arm. Insert the end of the arm through the shower flange and screw into the elbow. Turn in a clockwise motion to tighten. Do not over tighten.
Install the shower head to the end of the arm. Screw the pipe for the tub spout in the valve.
Attach back plate and escutcheon to the wall and install the volume control handle. Follow the product manual for the installation and adjustment of the Rotational Limit Stop. This mechanism controls the flow of hot water and thus, the water temperature.
Turn the water on to check the temperature with the thermometer provided with the product. Make adjustments until the temperature reaches 120 degrees Fahrenheit. Secure the control knob with the screw. Snap the control knob cover into place.