Well of course, too much of anything isn’t good for you. But keep in mind that too much water is generally only case for people who are in extreme situations (heart failure, mental illness, etc) If you weigh less than 135, please drink only 112 ounces of water per day. Otherwise, your gallon a day will be great. Americans are CHRONICALLY dehydrated and when you cut out the soda, coffee and other liquid junk, you will find yourself needing and wanting the full gallon of water.