Bleach-based cleaners will kill mold and mildew (temporarily) but they will also kill your grout. Over time, these harsh products will turn your grout to chalk, and it will wash out little by little.
The best defense against mildew is prevention! Increase the ventilation in the room. Leave the shower door open after you bathe. Let the exhaust fan run at least 20-30 minutes after use. Open a window. The next best weapon is a squeegee. Run it over your tile before you step out of the shower to eliminate water hanging around inviting the mold and mildew spores to take root.
The best cleaners for tile and grout have a Neutral PH. That means it is neither too acidic or too alkaline and will not harm your tile or grout. Some of our favorites are sold by Aqua Mix: Aqua Mix Products
Sealing your tile and grout may also help. Check out the sealers at TEC Products. These water-based sealers allow moisture and air out but none in, helping starve mold and mildew. Or take the extra step to eliminate future growth altogether with new antimicrobial SHIELD. Check out PowerOfShield.com
You can always contact Leigh in our service department for more details!
Neuse Tile Service 
May 5, 2011 at 10:10 pm
If it doesn’t come clean, you’ll want to scrape all the grout out with a razor knife, spray some a disinfectant in the joint, let it completely dry for at least two days, and then re-grout with a grout containing a latex-additive.