A crack in the tub next to the drain can cause water to leak into the subfloor, eventually causing mold and the accompanying expense of removing it. If you have a crack near your tub drain, repair the tub with a fiberglass repair kit designed for bathtubs. Although the process does involve removing the drain, you don't have to be a licensed plumber to use a fiberglass repair kit.
Pry the strainer off the drain basket in the basin of your tub. Use a screwdriver to pry up the strainer. If your tub has a pop-up drain, skip this step.
Place a pair of needle-nose pliers into the cross-bracing inside the drain basket and place the screwdriver between the handles. Turn the screwdriver counterclockwise to turn the drain basket out of the drain. If you have a pop-up drain, this process is easier. Grip the pop-up tab with the pliers and turn the drain counterclockwise.
Remove all of the old plumber's putty from the drain, using the putty knife or scraper.
Mix the catalyst with the fiberglass resin, then place the fiberglass cloth into the resin. This will wet the cloth and make it stick to the tub's surface.
Place the fiberglass cloth over the crack. It is okay if some of the cloth extends over the drain hole .You will trim it later.
Press the fiberglass tight against the tub's surface with a fiberglass roller or squeegee. Wipe up excess resin with a rag dipped in hot water. Allow at least 24 hours for the resin to cure.
Trim the fiberglass around the tub drain with the utility knife.
Sand the surface of the fiberglass smooth with an orbital sander. Blend the edges of the fiberglass patch with the surface of the tub.
Wipe off the surface of the tub with a rag.
Place a bead of plumber's putty onto the bottom of your drain basket, then secure the drain basket into the drain. Wipe off excess plumber's putty with the rag. Allow at least 12 hours for the putty to dry.