Bathtub drain strainers are commonly referred to as bathtub drain plugs. They naturally rust over time from exposure to water, but bathtub faucet leaks hasten the rusting process. If the plug is not replaced, rust can eat holes through the metal, leading to water damage and expensive repairs. Replacing the drain plug also gives the bathtub a more updated look. Bathtub drain repair parts are available at most home improvement and plumbing supply stores. If you don't have any plumbing experience, you may wish to hire a licensed plumber to replace the bathtub drain plug to avoid damaging the bathtub's finish.
Unscrew the bathtub drain pop-up; use slip-groove pliers to grip stubborn pop-ups. Some bathtub drain pop-ups are lift-and-turn models or tiptoe models that are spring-loaded. On spring-loaded models, unscrew the plastic pop-up cap, and unscrew the pop-up with a screwdriver.
Unscrew the bathtub drain strainer from the bathtub waste shoe, using a bathtub drain removal and installation tool. If the cross-gates break or the bathtub drain strainer will not turn with the bathtub drain removal tool, insert a bathtub drain extractor and turn it clockwise to remove the drain strainer.
Clean the inside threads of the bathtub waste shoe with a small brass wire brush to remove corrosion, rust and debris. Clean around the bathtub drain strainer sealing surface, using a mild abrasive cleanser and a sponge.
Apply a bead of plumber's putty to the underside lip of the bathtub drain strainer. Knead the putty in your hand until it is soft; this allows the putty to adhere to the drain strainer.
Apply plumber's PTFE paste to the threads of the bathtub drain strainer.
Screw the bathtub drain strainer into the bathtub drain waste shoe, and tighten it with the bathtub drain removal and installation tool.
Remove the excess plumber's putty with a small screwdriver; use caution when removing plumber's putty to avoid damaging the bathtub's finish.
Screw the new bathtub pop-up drain plug into the bathtub drain strainer.
Fill the bathtub with water to the overflow, and check the bathtub drain for leaks.