A leaking shower door seal isn't just annoying, it can be damaging to your house. Water that seeps out of the shower has to go somewhere and it will find its way into every nook and cranny in your bathroom around your shower. Eventually this will lead to wood rot and mildew. You can cure this quickly and easily by installing new shower door seals to keep the water where it is supposed to be.
Scrape away any remnants of glue, putty or caulk along the shower door where you wish to install the seal. Use a plastic putty knife or drywall knife if you are worried about scratching the metal surface. Use a sharp utility knife or razor blade, carefully, on stubborn spots.
Apply rubbing alcohol to a rag. Wipe this rag up and down the edge of the shower door to remove any soap scum or mildew. Dry thoroughly.
Insert a tube of silicone caulk into a caulk gun. Trim off the end at the smaller diameter marked on the spout, usually 3 mm (1/8 inch), at a 45 degree angle.
Insert the tip of the caulk gun as close as possible to the inside channel of the door seal. Squeeze out a bead of caulk along the length of the door seal.
Pick up the seal and press it into place at the top of the shower door. Work your way down the shower door, pressing the caulk into place as you do so. If any silicone caulk squeezes out through the edge of the seal, try not to wipe it up or disturb it.
Insert any screws, on seals so equipped, through the seal and into the shower door. Secure by turning the screw clockwise with a screwdriver.
Wait for any silicone caulk that has seeped out over the edges of the seal to dry. Cut this away with a sharp razor blade.