3 gallons would be 13 litres or 24 pints??!!
Id say that would be detrimental not beneficial. The idea that a person needs to drink 8 glasses of water a day (2.5 pints or 1.8 litres) is an unsuported myth, and it originally meant 8 glasses of liquid, which was inclusive of all liquid contained in the food as well.
Of course, you do need much more water in a hot climate, but 3 gallons is not only excessive, its dangerous. YOu can die drinking too much water from disturbing the salt levels in your body, causing poor electrical conductivity in even more excessive amounts the lungs can fill with the excess fluid and drown you. And dont believe that thirst is a poor indicator of fluid levels, we have not survived billions of years with a faulty fluid measuring system. That said, drink more than you might expect to say on the safe side I guess.