Installing a new sink will upgrade the look and functionality of your kitchen. Before you can install a new sink, you have to remove the existing sink. Sink removal is similar in all types of countertop materials, including granite. When removing sinks from granite, you will have brackets and silicone caulk to remove. Undermount sinks on granite also will have glue holding the sink to the countertop. You will need an assistant to help you remove an undermount sink from your granite countertop.
Open the sink cabinet and reach inside to turn off the water-supply valves to the sink's faucet. Look for a shutoff valve on each water line running to the faucet handles. Disconnect the supply lines from the faucet by twisting the connections off the faucet stems with a pair of tongue-and-groove pliers.
Locate the retaining nuts that secure the faucet to the sink. Look for a retaining nut at each faucet handle and possibly one in the center. Remove the nuts and the washers from the faucet with a socket wrench. Ask your helper to pull the faucet off the sink from above.
Disconnect the sink trap from the drainpipe going into the wall, using a pipe wrench. The sink trap is the curved piece of pipe connecting the wall drain to the sink drain. Turn the slip nut counterclockwise to disconnect the pipe.
Remove the sink tailpiece pipe from the bottom of the sink basket with the pipe wrench. The tailpiece is the short straight piece of pipe connecting the sink drain to the sink trap. Double sinks will have two pipes going to a T-connection. Disconnect the two pipes at the sink drains. Pull the sink trap and tailpiece out of the cabinet and set them aside.
Look for the clips that secure the sink to the granite countertop. Each clip will have a screw that secures the clip to the sink and countertop. If you have an undermount sink, have your helper hold the sink up while you remove the clip screws with a Phillips-head screwdriver. If your sink sits on top of the counter, the countertop supports the sink.
Cut through the silicone caulk around the perimeter of the sink, between the sink and the countertop, with a utility knife. Slide a putty knife between the sink and countertop on undermount sinks wherever there is enough room. There is glue between the sink and the bottom of the granite countertop. Attempt to cut through some of the glue on at least two sides of the sink, using the putty knife.
Work from above the sink while your helper stays under the cabinet, holding the bottom of the undermount sink. Tap a block of wood with a hammer around the perimeter of the sink bowls to loosen the glue. You do not need to bang hard on the wood -- just enough to begin breaking the glue seal. Have your helper lower the sink and remove it from the cabinet.
Lift a top-mount sink straight up out of the countertop; since there is no glue holding it in place, it will lift out without difficulty.