Grout mildew in the shower or tub area is not a pretty site and not very inviting for you to use or to potential home buyers.
A toothbrush makes a great tool to clean grout mildew. Use along with a cleaning product that can remove mineral deposits and kills molds and mildew. Protect your hands with rubber gloves.
Follow manufacturers directions, most instruct you to spray grout and let sit for about 10 minutes. Then you can start scrubbing the grout lines. Rinse well.
Many still favor and old standby, T.S.P. Trisodium Phosphate Powder for cleaning grout. It is available in powder form or premixed in a spray bottle.
Vinegar also works well, use full strength and make sure to avoid taps and handles.
You can also use a daily shower spray product after showering, simply spray shower walls, liner, and corners to help prevent a build up of mineral deposits, soap scum, and mildew.
Or tiles can be sprayed with a mix of vinegar and water after showers to prevent mold growth. Mix about 1/3 vintager to 2/3 water in a spray bottle.
You can go a step further once grout is dry and apply a grout sealer following manufacturers directions.
Spray it on, let it sit for 10 minutes, and then go after that grout with the toothbrush. Once it's clean, keep it looking good by painting on some grout sealer, available at your local home store.
It will create a hard seal over your grout and prevent water from working its way in and causing mildew.
Updated March 16, 2012