Clean Mildew Off Bathroom Tile Grout

By James Dulley

October 25, 2018 4 min read

DEAR JAMES: The grout in my bathroom between the tile is discolored with dark mildew. Some of the tile is glossy, and some has a flat, dull surface. What is the easiest and safest way to get it clean? — Ryan T.

DEAR RYAN: Dark mildewed grout is common in most bathrooms and anywhere else where there is tile and constant moisture. Even though the rest of the bathroom is clean, the discolored grout makes the entire bathroom seem unclean. Luckily, it does not damage the structural integrity of the grout, so when you finally get it cleaned, it will be as good as new.

It helps to understand the source of the mildewed grout so you can avoid it in the future after you get it cleaned. Without proper care, it will quickly return. Mildew is actually a living organism that survives on minute organic particles, such as flakes of skin, soap and oils as well as moisture.

It will be difficult to ever eliminate all the organic particles in a bathroom, but you can control the moisture level. The microscopic spores which the mildew sends out can stay dormant for a long time, so you must be conscientious about keeping everything drier. Dry off the shower walls and leave the shower curtain/door open.

Some of the stains you see may be caused by hard water deposits, and they may also be spread over the tiles themselves. These are a bit more difficult to clean off than the mildew, but they are easy to keep from returning. These hard water deposits, usually calcium, can be dissolved with white vinegar.

To remove the calcium deposits and stains, saturate some paper towels with vinegar. Place the wet towels against the tiles and press them down so that they contact the entire surface. They should cling naturally and stay in place. It may take a while, but once softened, these stains can be washed away with a scrub brush and water.

The best type of scrub brush to use has stiff plastic bristles. The surface of ceramic tile is very hard, so the plastic bristles, even though they may feel stout, should not scratch the tile surface. Avoid abrasive cleaners because the tiny abrasive particles may scratch and dull the glossy tiles.

To remove mildew, wash down the tile and scrub it with a standard bathroom cleaner. This may remove most of the mildew if it is not too bad. A few bathroom cleaners to consider are Lysol Mist Away Daily Shower Cleaner, Comet Cleanser with Bleach, Tilex by Clorox, and Arm & Hammer Clean Shower.

After you have used the cleaners, dry off the tile. Put on rubber gloves and saturate some more paper towels with chlorine bleach. Open some windows so you have adequate ventilation. Place these towels over the tiles. Bleach will whiten the grout and also kill any mildew spores it contacts to minimize future mildew growth.

Once you are done with the cleaning, you will likely still have a few dark mildewed grout spots. Use Clorox Beach Pen Gel to clean these difficult spots. Use the pointed end and squirt the bleach gel over the grout. Follow the instructions on the package and it should whiten even the stubborn spots.

Send your questions to Here's How, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit To find out more about James Dulley and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at

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