How to Change a Washer in a Faucet
Turn the water off to your home. You are going to have to remove your faucet entirely to change the washer, which means some of your pipes will be exposed. Turn the water off by locating the water line coming into your home and turning the knob all the way counterclockwise. This prohibits water from coming into your home.
Find the faucet that needs a washer replacement, and turn it on to release any excess water. Since the water is turned off, the faucet should run dry fairly quickly.
Remove the "hot" and "cold" caps that cover the handles of your faucet by sliding your screwdriver underneath one end of each cap and flipping it off. If your faucet only has one handle, simply remove the one cap. These are going to reveal screws.
Unscrew the screws that were under the "hot" and "cold" labels. This will allow you to actually pull the entire faucet away from the wall. Do this carefully because you do not want to damage any plumbing. This will reveal the remaining two pieces of the faucet, which contain the washer.
Disconnect the remaining 2 pieces of your faucet with your wrench. Inside the one end, you will see a round, black washer most likely. Use your screwdriver to pry the washer out. If the washer is worn out, has holes or appears damaged, you will need to replace it.
Replace the old washer with a new one by slipping it right into the recess that you took the damaged one from. Now, following these directions in reverse, reconnect your faucet, turn your water back on and make sure your new washer has stopped the leak.