A good indication that you are in water balance or close to it, is a natural, periodic thirst. The average person loses about ten cups of fluid a day through breathing, perspiring, and just keeping the body going. Milk, juices, soups, herb teas and decaffeinated coffee can count toward your total. Caffeinated beverages don't count because they actually use the body's water supply. If you don't get enough fluids, you become dehydrated.
Some people get headaches.
In extreme cases, dehydration can be deadly. This can happen when you change from a standing to a sitting position. The stoma that is nearly round when you are lying down or standing may be oval when you sit down. This may be a source of a leaking problem and merits some thought. Remember, the stoma is a portion of the intestines brought to the surface of the abdomen.