In older homes the bathtub may have a hot and cold faucet handle which can be dangerous and scald young children. To replace an older two handle faucet with a single anti-scalding faucet, a new cover place, and access to the plumbing is all that is required.
First, turn off the water supply lines, both hot and cold water lines. After the water is off, remove the small end caps from the handles and with a screwdriver remove the screw and then each handle. With a pair of channel lock pliers and a soft cloth, unscrew the spout, being careful as to not scratch it. After this is removed, using the same pliers, remove the shower head and pipe.
Now, from the back of the tub, the copper supply lines will need to be cut and all the pipes from the spout, faucets and shower head should be removed. New copper pipes need to be re-fitted and used to get a good solid leak free conversion. But centering the new handle and marking, cut a hole from the tube side to mount the new mixer handle. Remember to be careful if the wall is tiled and us the proper drill bit.
The new handle mounts from the rear of the tube and all copper piping needs to be dry fit before soldering all the pipes for a proper fit. After the initial fitting, soldering the pipes with a lead-free solder and make sure all pipes are secured per the new faucet manufacturers specification. When all the plumbing is complete, go back to the inside of the tube for final installation.
From the front now, you will see the new handle in the center of the tub and two empty holes, one on each side. This is where the new cover plate will install covering the new handle assembly and the empty hole for a nice clean professional finish. Use the instructions to mount the cover plate and caulk as required. Carefully line up the spout and with a soft cloth and pliers, tighten the spout making sure the output ends up pointing down.
Following the same procedure, install the shower head finished pipe and head. The last few finishing touches are the cover to go over the mixer valve sticking out the cover plate and then the handle itself that will screw on the end of the valve and a small cover cap to hide the screw. With everything in place, turn on both supplies and look for leaks and then try out your new bathtub faucet. Also note, the water temperature will not change when the toilet is flushed now due to the new anti-scalding valve.