Step 1
Clear out the area under the sink to give yourself better access to the underside of the faucet because this is where the washer and brass nut reside.
Step 2
Locate the washer and nut by looking up at the bottom of the sink counter. Find the nut and fit your wrench to it. If necessary to gain better access to the nut, turn off the water valves on the supply pipes under the sink, and unscrew the supply tubes that run from these pipes to the faucet.
Step 3
Turn the nut clockwise several turns or until you feel the tension increasing on the nut. If it is not possible to turn the nut with a regular wrench, use a basin wrench, which has a longer handle and a pivoting head. This wrench is designed specifically to unscrew faucet nuts.
Step 4
Check the faucet above the sink by gently pushing it backward and forward once you think the nut is tight. If the faucet is still loose, tighten the nut again until the faucet no longer moves.