If you change the washer, the faucet still drips, then there may be a problem with the faucet valve seat. A damaged washer may cause the seat of the faucet to become worn out by the metal core, or the deposition of chemicals in the water may form a residue that prevents the gasket from being fully compressed with the valve seat.
How do you fix the broken faucet seat? Of course, you can change the whole faucet. Another option is to change the faucet only. If you have the right tool, called the seat wrench, it's easy to remove the old seat. Insert the seat wrench into the seat and pull it in an anticlockwise direction. Once you remove the old seat, make sure that the new seat you bought is the same as the original one. If the seat can not be removed, it can insert a slide into the proper position of the valve seat and valve seat with the old seal. Two types of seat roller or sander that can flatten worn seats.
Another option is to use a seat roller or sander, a cheap tool to flatten worn seat. When using this tool, be careful not to take too long or use too much force, because the seat is made of soft metal, and you can easily wear it too far.
When using a sander, first remove the faucet spool and insert the seat roller downwards into the seat in the faucet body. Turn the tool clockwise several times with moderate force. Then wipe the metal scraps off the valve seat with a cloth.