Shut off the water supply valves under the sink to prevent water flow during removal.
Place a bucket directly beneath the drain to catch any residual water in the pipes.
Use an adjustable wrench to loosen and remove the locknut securing the drain tailpiece.
Carefully lift out the drain tailpiece from the sink opening, allowing water to drain into the bucket.
Loosen and disconnect the P-trap from the drain tailpiece and remove it from under the sink.
Unscrew and remove the drain flange from the top of the sink using a putty knife if necessary.
Clean the area around the drain opening thoroughly to ensure a good seal for the new drain.
Inspect the old drain components for cracks or damage; replace if necessary.
Apply a bead of plumber's putty around the underside of the new drain flange to create a watertight seal.
Insert the new drain flange into the sink opening from above, pressing firmly into place.
From underneath, screw on the locknut onto the drain tailpiece to secure the flange.
Reconnect the P-trap to the drain tailpiece, ensuring all connections are tight and aligned.
Tighten all nuts and fittings securely to prevent leaks.
Restore the water supply and run water into the sink to check for leaks around the drain and P-trap.
If leaks are detected, tighten fittings further or reapply plumber's putty as needed.