Some shower faucet models still use a valve stem assembly to regulate the water that enters the faucet. When a part on the valve stem assembly, such as a washer, wears out, you simply remove that part from the valve stem instead of replacing the plastic cylinder found in cartridge-style faucets. Since the washer is made of rubber, it will break down and become brittle over time, especially if the valve controls the flow of hot water through the faucet.
Close the main water valve in the house, cutting off the flow of water to the shower's faucet. This main valve is often located near the water heater. Turn on the faucet all the way to ensure no water is left in the pipes, then turn off.
Remove the screw that holds the shower's control handle in place, using either a Phillips screwdriver or an Allen wrench. The screw will be located in a small recess on the side of the handle or under a plastic decorative cap in the middle of the handle.
Pull the handle off the valve stem, or--if the handle is stuck--clamp a handle puller to the back side of the handle and turn the puller's centre post to the right until the handle comes off. Use a pair of pliers to twist any plastic covers or metal nuts off the valve stem.
Remove the clip--if one is present--on the side of the valve, using a small flathead screwdriver. Turn the valve counterclockwise in the faucet with the pliers until the valve comes free from the faucet.
Use a screwdriver to remove the screw at the end of the valve, then remove the washer from the valve assembly. Slide the new washer onto the valve and replace the screw.
Reassemble the shower's faucet by reversing the steps you took to take it apart. Open the house's main water valve by twisting counterclockwise.