My 29 years old brother pisses in bottles?

I know this sounds gross, but i honestly cannot find what kind of behavior this is. I have searched the interent and i know he is ADHD, but this is beyond what scientist can figure out. Ever see that movie Aviator. And Howard Hughes was a recluse for months and he stored huge bottles of pee. Well my brother does this and found a gallon jug full before, and also like 7 water bottles at a time stored in his closet. Anyone know what kind of psychological beahvior this is?