Removing an undermount sink will require the assistance of a helper. Undermount sinks are secured to the bottom of the granite countertop with sink clips under the countertop, rather than having the sink edge rest over the countertop. You will need to be able to hold the sink against the countertop as you are removing the sink. Sink removal will require you to disconnect the sink drain plumbing and the faucet before you can begin removing the sink.
Shut off the water supply valves under the sink. Remove all of the contents from the sink cabinet and place a bucket under the sink drain plumbing.
Locate where the water lines connect to your faucet. Use a pair of channel lock pliers to loosen the connections and remove the water lines from the faucet.
Remove the retaining nuts that secure the faucet to the sink by turning the nuts counterclockwise with a wrench. Depending on your faucet type, there will be either one or three nuts. Ask a helper to pull the faucet out of the granite countertop.
Push the bucket under the slip nut that secures the sink drain pipes to the house drain pipe coming from the wall. Loosen the slip nut with a pipe wrench until you can turn the nut by hand. Twist the nut off the sink drain pipe and push the nut toward the wall. The bucket will catch any residual water in the drain pipes.
Remove the sink drain pipe from the sink drain. Turn the connecting slip nut counterclockwise with a pipe wrench. Pull the sink drain plumbing out of your work area.
Lay a piece of scrap lumber across the top of the sink. Ask your helper to insert a rope through one of the sink drains and then you take the rope end and insert it back up the second sink drain if you have a double sink. If you have a single sink, insert the rope between the cross piece of the sink drain and insert back through a separate cross piece. Tie the rope around the board. This will hold the weight of the sink as you loosen and remove sink clips.
Score the caulking around the edge of the sink where it meets the bottom of the granite countertop with a utility knife. Locate each of the sink clips that secure the undermount sink to the countertop.
Remove the screws securing the clips with a Phillips-head screwdriver. Start at each end of the sink then the rear of the sink. If necessary, ask your helper to pull up on the board or rope to keep the sink from bowing down. Remove the screws securing the front clip. Hold the bottom of the sink with both hands so that the sink is against the countertop. Ask your helper to untie the rope from the board and remove the rope and board off the countertop.
Lower the sink carefully until your helper can grab the sink from above. Angle and maneuver the sink through the hole in the countertop.