How to Remove a Stuck Bathtub Drain Stopper Assembly

Begin by clearing the bathtub of all bottles, mats, and toys. Ensure the tub surface is dry. Place an old towel or thick rag in the bottom of the tub to protect the finish from accidental scratches from your tools. Use a flashlight to get a clear view of the drain stopper, its base, and the set screw area. Put on your protective gloves.

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.

First, locate the small set screw on the side of the stopper's main knob. Use an appropriately sized Allen wrench or a small flathead screwdriver to turn this screw counter-clockwise. You may not need to remove it completely, just loosen it by a few turns. Once the screw is loose, hold the body of the stopper (the larger cylindrical part) firmly with one hand or with a pair of pliers wrapped in a rag to prevent scratching. With your other hand, grasp the top knob and turn it counter-clockwise to unscrew it from the stopper body. If the knob is removed and the stopper is still stuck, you will be unscrewing the entire stopper assembly from the central post in the drain.

If the stopper cap will not separate or if the entire drain flange assembly is what's stuck, you will need a specialized tool. A drain key (also called a 'smart dumbbell') is designed for this. Insert the drain key into the drain opening; its stepped ends are designed to fit various drain sizes. Ensure it is seated firmly against the crossbars inside the drain. Attach an adjustable wrench or a large pair of pliers to the top of the drain key. Apply firm, steady, counter-clockwise pressure to the wrench to break the seal and unscrew the entire drain flange from the drain shoe below. This may require significant force, especially if sealed with old, hardened plumber's putty.

Once the stopper or the entire drain flange has been removed, you will likely see old, crumbly plumber's putty, hair, and other debris in the drain opening and on its threads. Use a plastic putty knife or a flathead screwdriver to carefully scrape away the old putty. Use a stiff wire brush to thoroughly clean the female threads inside the drain pipe. Finally, wipe the area clean with a rag and some mineral spirits or an all-purpose cleaner to ensure a clean surface for installing the new drain stopper.