Before applying an epoxy glue sealant to a plastic gas tank, the tank must first be emptied of its contents and allowed to air dry.After that, using sandpaper with a coarse grit, sand the area surrounding the hole or crack, and then wipe the area with a cloth that has been soaked in rubbing alcohol.The next step is to thoroughly combine the epoxy glue, spread it over the hole, and then adhere a patch made of fiberglass over the epoxy.