If you find that your shower faucet stem leaks regularly when you are taking a shower, or if the parts of the stem have begun to wear down through regular use, then you will need to install a new one. Since replacing a shower faucet stem is not a very difficult task, rather than call a plumber, you should be able to perform this simple task completely on your own. You will need a few basic household tools, and some free time in which to complete this project.
Step 1 - Turn off the Water Supply
Before you begin any repairs in your bathroom, it is always a good idea to turn your water off at the mains. You might consider just shutting off the water to your shower, which will allow you to run water to other parts of the house, but this is often a false saving and will leave you vulnerable to water leaks. Turn off the water supply using your key or by twisting the valve using your wrench. Run the water from the shower after to ensure the pipes are completely empty before beginning your work.
Step 2 - Remove Faucet Handles
At the tip of your faucet handle, you will be able to see a round disc. This is the cover that can be removed using the flat tip of your screwdriver. Once this has been popped off, you should be able to see a large screw securing the handle in place. Undo this screw, and set it off to one side. Then, take off the handle, wiggling it back and forth if it seems stuck on the stem. You should be able to see a flange behind the handle as well; this also needs to be removed.
Step 3 - Reveal the Stem
On many faucets, there will be decorative escutcheons hiding the stem. Cut away any caulking around them with a utility knife and twist counterclockwise to unthread them from the base. Pull any trim rings off of the stem as well, if necessary.
Step 4 - Remove the Stem
Now you will be able to see the faucet stem. Clear any dirt, debris, or caulking from the hole to give yourself a better look at the entire thing. On each side will be a hexagonal bolt. Use a proper-fitting socket and turn it until the bolt is out. You may sometimes find that the bolt is actually fitted into the wall, in a recess. A socket wrench should still work with no trouble.
Step 5 - Replace the Stem and Put the Faucet Back Together
Once the bolts are free, the old stem can be taken off. Take your new shower faucet stem, and make sure that it is a suitable match for the other. You need a perfect stem double in order to prevent leaking.
Push the new stem into the wall, and tighten the bolts back up. Replace the escutcheons and the flange next, and then add caulking around the areas that need a proper seal. Give the caulk a short amount of time to set, just to be certain you don't ruin your bead by continuing.
Finally, screw the faucet handle back into place and refit the handle cover.
Step 6 - Test
It's always a good idea to be certain your job has been completed successfully, so switch the water main back on and give the faucet a quick inspection for further leaks.