Changing the fixtures on your bathtub, such as the faucet and hot and cold knobs, is relatively quick and easy. However, it's important to know what type of fixtures to buy, how to remove your old fixtures and how to properly install the new ones so that your plumbing works correctly.

Buying New Fixtures

First, you must determine what type of faucet you have now so that you will know what type to buy. Check under the faucet. If there's a setscrew visible, you have a slip-on faucet. If there isn't a screw, you have a screw-on faucet. Just as bathtub faucets aren't universal, hot and cold water valves aren't universal, so you should pay close attention to your hot and cold water valves when you buy new ones. For example, you may need to buy two knobs or one large knob to switch between hot and cold water. If you buy the wrong type for your bathtub, you may need to hire a plumber to change your hot and cold water lines. You should also measure your bathtub fixtures so you know what size to buy. You should know the dimensions of the plates that cover the neck of the faucet that help attach it to the wall or tub and conceal where the fixtures join your plumbing pipe. The new fixtures that you buy should be the same size or slightly larger than your old fixtures so that the holes in your tub or wall that allow for the fixtures won't show.

Removing Old Fixtures

Before you remove any fixtures from your bathtub, you should turn your house's main water supply off to avoid leakage. To remove your hot and cold water knobs, you will probably have to pop a cover plate off the front of the knob to reveal a screw. Unscrew the screw, and then remove the knob. To remove a slip-on faucet, loosen the setscrew under the faucet, and gently pull it off the water pipe. To remove a screw-on faucet, twist the faucet counterclockwise until it is free from the water pipe.

Installing New Fixtures

To install a new slip-on faucet, slip the faucet onto the water pipe and tighten the setscrew underneath. To install a new screw-on faucet, screw the faucet onto the water pipe. In some cases, your water pipe may be too short, so you should get an adapter pipe from your local hardware store. If you need to add an adapter pipe, you should wrap plumber's tape around the piping to ensure a tight seal. If you can't get the faucet screwed on tight enough, you can use a plumber's wrench for extra leverage, but you should wrap a cloth around the new faucet first to prevent the wrench from scratching it. Most hot and cold knobs simply screw on. Certain types of hot and cold knobs may come with decorative plates to hide the screws, which simply pop on.

Source:

Bathroom and Kitchen Guide: How to Change a Bathtub Faucet in 8 Simple Steps

HGTV: Shop Smart for a Shower and Bathtub

Reader's Digest - The Family Handyman: How to Replace a Bathtub Spout