Do you drink enough water?

It is often said that we don’t drink enough water and i am certainly guilty. The more I read about the subject the more convinced I am that it is a simple solution to better health. I try to drink at least a gallon a day.
From about.com
Symptoms of mild dehydration include chronic pains in joints and muscles,lower back pain, headaches and constipation.
A good estimate is to take your body weight in pounds and divide that number in half. That gives you the number of ounces of water per day that you need to drink. For example, if you weigh 160 pounds, you should drink at least 80 ounces of water per day. If you exercise you should drink another eight ounce glass of water for every 20 minutes you are active. If you drink alcohol, you should drink at least an equal amount of water.