Step 1 · Preparation and Old Drain Removal
Begin by clearing all items from the cabinet under the sink to create a clean workspace. Turn off the hot and cold water by turning the knobs on the shutoff valves clockwise until they stop. Place a bucket directly under the P-trap. Use channel-lock pliers to loosen the large slip nuts securing the P-trap to the sink's vertical tailpiece and the horizontal trap arm going into the wall. Once loose, finish unscrewing them by hand. Carefully lower the P-trap, emptying its water and debris into the bucket. Next, use the pliers to loosen the large locknut holding the main drain body to the underside of the sink. While supporting the drain body from below, have a helper unscrew the drain flange from inside the sink, or reach in and do it yourself. Remove the entire old drain assembly. Finally, use a putty knife and a rag to scrape and wipe away all old plumber's putty and gasket residue from the sink's drain opening, ensuring a clean surface.