Many homeowners are unaware that glass shower-door frames have built-in holes and channels that allow accumulated water to drain back into the shower. Unfortunately, these features are often covered up with caulk by installers. The result is that water pools up inside of the door frame and can eventually leak out of the shower. If this is happening to your shower enclosure, the door frame needs to be fixed.
Cover the shower drain with masking tape to prevent small chunks of caulk from falling in and clogging the drain.
Strip any caulk from the inside of the shower-door frame using a putty knife or razor blade (porcelain showers only), then use a screwdriver to scrape off any excess.
Check the drainage holes and channels for blockage. If they are blocked, use a large sewing needle to pick out any caulk. If the channels are blocked with built-up soap scum, scrub the area with an appropriate remover.
Inspect the rubber seals and runners around the shower door for damage. If any rubber parts are badly worn, torn or missing, replace them.
Strip the caulk from the outside of the shower door, following the instructions in Step 2.
Apply a fresh bead of 100-percent silicone caulk along the outside of the shower-door frame. Allow it to cure for 24 hours before using the shower.