Drinking too much tea can cause kidney stones. All that sediment you see in the cup ... that's just the tiny bit left over after you've slurped down the rest of it.
Tea's, powder drinks such as Kook Aid, those little Crystal Light water flavoring packets ... all that stuff in excess can cause kidney stones.
My mom used to make ice tea by the gallons. People loved it and they'd stop in for some throughout the day during the summer. Friends, neighbors, and guys my brother worked with in the Police department. It was a small town and everybody knew everybody.
She used a gallon pickle jar, all cleaned out of course, and made the tea in it. She'd boil it on the stove for a while, then mix it with water, sugar, and ice in the jug. It was so cloudy you could shine a flash light on the side of the jar and you couldn't see light through the other side. I drank it for years, and look at me ... I turned out ok. Right? ;-)