Over time and with use, different components of a garden tub will wear out, including the faucet. You may decide to replace the faucet simply because you want to change the look of your bathroom by changing out all of the hardware, or you may want to upgrade your basic faucet with a new faucet. Whatever the reason, you can replace a garden tub's faucet without specialized plumbing knowledge and without spending hours on the project.
Shut off all water going to the tub by turning the house's master shutoff valve to off. Open another faucet to drain any water from the pipes.
Twist the old faucet counterclockwise to unscrew it from its nipple. If the faucet will not move easily, wrap a thin piece of cloth over the faucet for protection and use a plumber's wrench to twist the faucet off.
Unscrew the faucet's nipple assembly, using the plumber's wrench. Wrap thread tape over the threads at both ends of the new faucet's nipple assembly, then use the plumber's wrench to screw the new nipple into the water pipe.
Apply a thin layer of silicone caulk around where the nipple assembly meets the tub's surface. Screw the new tub faucet into place on the end of the nipple assembly until the faucet is flush with the tub's surface.