When you say that if you stop drinking for 14+ hours you become "dry as a bone", but do you continue to urinate such large volumes, even if you havn't had anything to drink in a while? I second mal, that may be a sign of diabetes. Especially if you have an unquenchable thirst, not just drinking lots of water because it's good for you.
If you are drinking that much just for the health of it, too much may not be a good thing. People who drink way too much water may throw off their electrolyte balance, diluting their sodium, potassium and other electrolytes which are important for muscle function, especially heart muscle (though I'm not sure exactly how much you'd need to drink to hyperhydrate). Urine shouldn't be clear as water, there should be some yellow colouration to it. Maybe try adding some electrolytes to the water. Sports stores will sell sodium chloride athletes put in their water, both to help with water absorption to ensure rapid rehydration, and to make sure electrolyte balances stay in cheque.
Try cutting back on the water a bit, but if you can't stand doing that and you feel like you're getting dehydrated, or you still urinate the same volume regardless, go get checked out.
