I have no idea how your doing that? I use to work outside down here in SC and we're talking 100+ all day. I doubt I ever drank 2 gallons a day and most of it was getting sweated out of me. In my case 2 gallons spread over the day was probably doable but most people aren't faced with that kind of heat. On the other hand I was so use to the heat that I would go out for a 10 mile rollerblade with a 110 degree heat index no problem. Maybe I really under estimated how much I was drinking a day.
I still say your normal person does not need that kind of water in take. Also you know what you eat and supps can color your urine?