Sink drain lines are installed in two basic ways: through the floor, which is the through the wall, which is the approach used in most newer ones to make installing bathroom vanities and kitchen cabinets easier. Drain assemblies consist of three basic components. The tailpiece hooks to the bottom of the sink opening. A long elbow attaches to the house waste system. A simple trap joins the first two. Once installed, the trap is filled with water that prevents sewer gas from entering the house.
1. To remove a sink drain, first slide a bucket or pan under the trap to catch any spilled wastewater. Then loosen the two nuts that hold the P-trap in place. Use groove-joint pliers or a pipe wrench. Cover the jaws of each with a rag to prevent scratching the chrome surfaces.
2. Once the trap is removed, slide the escutcheon away from the wall; unthread the frictions nut that holds the drain elbow to the main waste line; and pull it and its the washer away from the drainpipe. Set aside the drain elbow. If this pipe is corroded, now is a good time to replace it.
3. The drain's pop-up stopper is operated by a knob on top of the sink. This knob is connected to a lift rod under the sink, which is joined to the pop-up linkage(in the side of the drain body/tailpiece) with a tension clip. To remove the clip, just squeeze the ends together and slide it off the pop-up rod.
4. After you disconnect the pop-up linkage from the side of the drain body/tailpiece, loosen the jamb nut that holds the drain gasket in place using groove-joint pliers. If the drain body/tailpiece spins, backhold it using a second pair of pliers.
5. Unscrew the drain body/tailpiece by turning the drain flange ring from above. (Having some help makes this job much easier.) Pull the drain body/tailpiece away, and lift the flange ring out of the sink drain hole from above. Clean up any putty residue from the where the drain flange ring was seated.