The average person needs to replace approximately 10 cups of fluid (2.5 liters) per day. (The average urine output for adults is about 6 cups, or 1.5 liters, per day. And people lose close to an additional 4 cups, or 1 liter, of water daily through breathing, sweating and bowel movements.)
Since food accounts for about 20 percent of your total fluid intake, this means you need to consume about 8 eight-ounce glasses of water or other beverages a day to be fully hydrated.
If you're exercising, you'll need to consume more water. For workouts under an hour, you'll likely need an extra 1 to 3 cups of water. Intense exercise lasting more than an hour requires more fluid intake. How much additional fluid you need depends on how much you sweat during exercise, and the duration and type of exercise.
You should be drinking filtered water until your urine is a pale yellow or clear, which will ensure you're drinking enough.
Water gives you energy as it hydrates the cells and allows the organs to function optimally. It also flushes toxins from the body and encourages a healthy digestive system.
Drinking water is also related to weight loss and maintaining a healthy weight, because water will keep your metabolism high. When your body detects that you are dehydrated, it will naturally slow your metabolism to protect you.