Step 4 · Remove the Old Faucet
From underneath the sink, use the basin wrench to loosen and remove the mounting nuts that secure the old faucet to the sink deck. These can be metal or plastic and are often corroded. If they are stuck, apply penetrating oil. Once the nuts and any washers or brackets are removed, go to the top of the sink. Gently pull the old faucet assembly straight up and out of the mounting holes. You may need to use a putty knife to gently pry it up if it's stuck down with old plumber's putty or caulk.