Whenever tile grout and moisture get together, a science experiment begins. Soon your pretty white grout starts getting small black patches. The patches soon start hooking up with each other, creating a whole mildew network that looks ugly and unsanitary. Once it's there, it's tough to remove. No matter how hard you scrub, some mildew and discoloration remains -- unless you know the Carey Brothers' family secret recipe for fighting mildew. For almost any washable surface, add 1 quart of liquid laundry bleach to 3 quarts of warm water. Then add 1 cup of powdered laundry detergent -- a little less if concentrated -- and mix well. Scrub this solution on the fungus-darkened area, keeping it wet until the black mildew turns white. When it clears up, the mildew fungus is dead. Wear rubber gloves, protect your eyes and have plenty of ventilation. And that's the On The House tip for today.