Have you ever had or have mildew stains in the grout lines of your shower area. They are tough to get out, better grab a grout brush, possibly some bleach and get to scrubbing. A product that I have found to work extremely well and does what it says on the bottle is X-14. You can spray the mildew stains, let the chemical go to work for about 2-5 minutes and then wipe away the grime. Fairly inexpensive product, but cannot be found in your local stores. Mostly found online such as Amazon.