Things You’ll Need:
* Tub drain wrench
* Plumber's putty
Purchase the appropriate tools and equipment. For this repair, you'll need a tub drain wrench. They are available at any hardware including Ace, Lowe's and Home Depot. You will also need plumber's putty and a new drain.
Remove the plug. Put the plug down. Using pliers, grab onto the plug and twist it in a counter-clockwise direction. Continue twisting it until the plug comes out of the hole.
Use the tub wrench. Place the wrench into the hole, and using a counterclockwise motion, unscrew the drain flange and pull it up and out.
Prepare the drain flange for installation. Smear plumber's putty under the flange rim. In order to ensure a water tight seal, this is a necessary step.
Install the new drain. Using the tub wrench, twist the drain into the hole using a clockwise direction.
Screw in the stopper. Twist the stopper in a clockwise direction until it is fully inserted into the new drain.
Test your bathtub drain-stopper. Turn on the water and allow your tub to partially fill up. If it holds water, your repair is successful. If not, try again using the previous steps.
has step by step with pictures.