I just removed the caulking around the bottom of my shower stall (where the floor tile meets the wall tile). The caulking showed little or no evidence of mildew, however the underlying grout has mildew. What do I do, merely disinfect the grout and allow to dry and then re-caulk or do I have a bigger problem here? I don't want to make a costly mistake.
Thank you, in advance, to anyone out there who could give me some helpful advice.

Hi Marona,

Once you have mildew, even if you are able to thoroughly clean the grout, you will always have to battle it. Mildew send out millions of tiny spores (seeds) that can lie dormant for a long time. Once moisture and their food source is present, mildew pops to life and send out more spores into the air.

In addition to the mildew, you may have some hard water stains (primarily calcium deposits) on the grout. You will find this out as you attempt to remove the mildew because the cleaning procedures for the two are different. Also, you may have to treat the dull tile differently than the glossy tile.

First, go to your hardware store and buy a good quality scrub brush with stout plastic bristles. The bristles may feel very stiff, but they should not scratch the very hard tile surface. Use abrasive cleaners, even mild ones, as a last resort. Repeated use of these can dull all the tiles.

On your way home, stop at the supermarket and pick up some standard chlorine bleach, white vinegar, rubber gloves and rolls of paper towels. You might also check out some of the common tub and tile cleaners that indicate that they are effective for cleaning the grout too.

Almost all of the common ones are safe to glossy ceramic bathroom tile. The dull, softer tile may or may not be a different story. You should test the cleaners on small areas first or contact the company and ask them about it.

Here are a few of the common bathroom cleaners to consider and to call about - Mist Away by Reckitt & Colman (800-228-4722), Comet by P&G (800-926-9441), Tilex by Clorox (800-227-1860), and Original Clean Shower by Church & Dwight (800-617-4220).

Use one of the above cleaners and the scrub brush to remove as much of the mildew and any scum on the tiles. If you are having problems cleaning the tiles, it is probably hard water deposits. These are as hard as a rock.

Soak some paper towels with white vinegar and lay them over the tile and grout. The wet towels will cling to the vertical wall tiles. It will likely take many hours to soften the deposits. Check the paper towels every two hours to make sure that they are still wet with vinegar.

Rinse the walls thoroughly to make sure that all the vinegar is off and dry them. Wear your rubber gloves and saturate more paper towels with chlorine bleach. Place these against the grout and let the bleach do its whitening work for hours. This will also kill all the mildew.

In order to minimize the future growth of mildew on the grout, take away its nutrients and moisture. Rinse the walls when you are done showering and then run a shower squeegee over them. It only takes about 30 seconds. Leave the shower curtain or door open to hasten the drying time.

Tools and materials required: scrub brush, shower squeegee, paper towels, cleaner, vinegar, bleach

Good luck, Tom

Thanks for all the helpful advise. I didn't know where to begin with the mess I encountered in my shower. I'm so glad I found this sight. A special thanks to you, Tom, for your very detailed response. I'm off to pick up my supplies...
Thanks again.

As for mildew on grout in tubs and showers, one important issue is the condition of the wall behind the tiles. There was a time when green gypsum board was the tile backer of choice in tubs and showers, but sadly it had a ten year life. Grout is porous, and gypsum is even more porous! Thus if you have a mildew problem, very hard cleaning with bleach and a scrubbing brush may have you knocking out tiles and exposing a spongy wall infested with mold and mildew -- a very unhealthy bathroom indeed.

For those fortunate enough to have proper tile backing, such as an original mud job (cement on wire lathe), or Wonderboard/Durock, or the new composite tile backer board, then mildew can be easily chased away with occasional bleach scrubbing, or special bathroom cleaners for mildew.

If grout is old and broken, but the wall is sound, it can be carefully removed with a grout saw and then the wall can be regrouted. I would highly recommend epoxy grouts, which do not mildew. BUT a word of caution: please follow directions exactly, or have a professional do the epoxy grout, because it is a bear to clean off the tiles. Also, if you must use caulking in a tub or shower, it is best to use a polymeric caulking such as Geocel (clean with paint thinner, not water). NEVER use pure silicone caulking in a shower; it doesn't stick to anything but your fingers, and it makes a mess, and then when it dries it discolors and peels off like a bad sunburn.

Be careful re-grouting if the wall has mildew behind it because the moisture of the new and fresh grout that is being applied will absorb the dirty particles that are in the Sheetrock, seep them through, and the new grout will be stained before it even dries. It happened to me once. If your bathtub's grout has been cracked for a long time changes are the immediate Sheetrock behind it is rotten and dirty. By that point it is simply better to take it all out, tile and Sheetrock, and start from scratch with new Sheetrock (latex coat it while at it before putting tile) and new tile.