Black Stains on Grout
Hi - I had a new shower installed about 18 months ago which included full ceramic tile around the walls and a fiberglass base. I try and take excellent care of the keeping the shower clean - I squeejy all the tile walls and glass doors after EVERY shower and make towel off the grout joints where the tile meets the fiberglass base. Yet - in certain areas of the shower I get some annoying black stains on the grouted areas. I guess its mildew but am unsure. Its usually in the same spots. I clean them with a brush but they don't go away. I even caulked over those areas and they keep reappearing a few weeks later so I know its something I must be causing and not bad grout or workmanship. I keep wondering if there is something else going on that maybe I'm causing. The one thing that comes to mind is that I use a tile cleaner once per week called Kaboom. I sray it on the tile; apply a sponge and then let it sit for 3 -5 minutes. Could this be the issue? Could I be leaving it on too long (bottle says 3 minutes). Could it be ventilation? I do have a fan in the bathroom. If anyone has any incite, I'd appreciate it.