Step 2 · Apply Penetrating Oil

Generously spray or apply a penetrating oil around the base of the drain stopper where it meets the drain flange. Also, apply a small amount directly onto the set screw on the knob. Allow the penetrating oil to sit for at least 15-30 minutes. This gives the oil time to seep into the threads and dissolve the corrosion and mineral deposits that are causing the stopper to be stuck.