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This will install a new sink drain and connect the drain to the waste pipes, allowing wastewater to drain directly from the sink into the drainpipes. Use a pipe wrench to loosen and remove the nut securing the drain flange. Then you can push the sink drain up through the sink for removal. Scrape the putty off using the putty knife. If the putty is very hard and difficult to remove then you should use a razor to remove the excess. After cleaning off the chunks of putty use a scrubbing pad and water to scrub the area clean. If the putty is too difficult to remove, use rubbing alcohol or spirits to remove the putty. The drain will come with a washer when it is purchased. Move to the underside of the drain and place the washer over the threads and secure with the large nut that comes with your drain. Tighten the nut as securely as possible using tongue-and-groove pliers.  It may help to have someone hold the drain from the top so it does not move around. Remove excess putty after securing the drain. This will connect the drain to the elbow pipe. It should be long enough that it is at the same level of the pipe it needs to be connected to. Hand-tighten the tailpiece to the sink drain to secure the piece. Attach the pieces together to create the bend in the pipe directing towards the adjacent sink. Use the connector pipe to connect the elbow piece to the T-fitting on the adjacent sink. The connector piece might need to be cut down to the correct length depending on your sink. Use the nuts and washers provided with your pipes to secure the pieces together using the tongue-and-groove pliers.
Use this method if you have removed your garbage disposal and do not wish to install a new one. Remove the nut securing the drain flange to remove the sink drain. Clean the putty around the drain hole with a putty knife. Secure the flat washer to the underside of the drain. Find the PVC drain tailpiece. Attach the elbow pipe to the tailpiece. Connect the connector pipe to the elbow and the adjacent sink.