It is not often that your bathtub overflow gasket needs to be replaced; its lifespan is approximately 10 years. This seal prevents water from entering behind your bathtub around the overflow drain. The overflow gasket is a rubber ring that fits in the opening behind your overflow cover. By removing the cover you will have easy access to your gasket. With a few simple hand tools, you can replace your own gasket without the need to hire a plumber.
Cover the bathtub drain either by closing it with the stopper or by placing a towel over it--it's all too easy to drop or knock one of the screws into the drain.
Loosen and remove the two screws that are holding the overflow drain cover plate in place. The cover plate must be out of the way in order to access the gasket. Pull the cover plate off and set it aside with the screws.
Use pliers to grasp the overflow gasket. Pull straight out to remove it. If you have trouble removing the gasket, spray it with a lubricant to help loosen it.
Scrape the area behind the cover plate to remove old caulking before you install the new gasket.
Insert the two screws that hold the cover plate into the holes in the drainpipe to push the pipe back far enough to install the new gasket. The screws do not need to be fully tightened at this point, and you do not need the cover plate for this step.
Insert the new gasket into the overflow hole with the thin edge facing up. Press the gasket firmly into place, taking care not to press against your overflow pipe.
Remove the screws and apply a bead of silicone caulk around the perimeter of the gasket.
Hold the cover plate in place and insert the two screws. Tighten the screws to hold the drain overflow cover plate in place. Take care not to over-tighten the screws; they only need to be tight enough to hold the cover plate. If you over-tighten the screws, you can crack the drainpipe.