Which water's which

Artesian water: From an underground aquifer. Examples: Fiji, Voss and Hawaiian Springs.

Distilled or purified: From a tap and treated to remove contaminants. Examples: Dasani, Aquafina and Penta.

Enhanced water: Usually distilled and enhanced with vitamins, minerals, oxygen, electrolytes or herbs. Examples: Glaceau Vitamin Water and Essentia.

Fitness water: Usually distilled with added electrolytes, sugars, caffeine and/or herbal stimulants. Examples: Propel, Hansen's E20 Energy Water.

Mineral water: From an underground source that contains naturally occurring dissolved solids, such as calcium, magnesium, potassium. Examples: Evian, Contrex

Sparkling water: With natural or artificial effervescence. Examples: Perrier and Pellegrino (natural), Club Soda (artificial).

Spring water: From an underground source that bubbles to the surface. Examples: Poland Spring, Icelandic Glacial.

- Rosemary Ford

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Am I dehydrated?

The guideline that everybody should drink eight glasses of water a day is inaccurate, said Douglas Casa, PhD., who studies heat and hydration issues at the University of Connecticut. Everybody's water needs are different.

"If you're lying on a couch all day in an air conditioned environment, you're going to have a lot less need than somebody who's out exercising for four or five hours in the heat," Casa said.

Here are two quick tests to find out if you're drinking the right amount of water:

1. Weigh yourself naked before and after exercise. If you gained weight, drink less water next time. If you lost weight, drink more water next time.

Your goal should be to lose no more than 2 percent of your body weight to sweat during an exercise session. A person who weighs 100 pounds shouldn't lose more than 2 pounds. A 150-pound person shouldn't lose more than 3 pounds. A 200-pound person shouldn't lose more than 4 pounds.

2. Check your urine color. If it's light like lemonade, you're well hydrated and might want to drink a little less fluids, Casa said. If it's dark like apple juice, you need more fluids.

- Julie Kirkwood

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A splash of skepticism

The labels on bottled water can be misleading if you don't look closely.

Far from being a cleaner version of what comes from the tap, products marketed as water often contain sugars, salts that only athletes need, and caffeine. Here are some things to look for on a water label and what they mean:

Guarana - This is an herb put in some waters for an energy boost. It is actually a stimulant similar to caffeine and will keep you up at night if you drink a lot of it. Some waters, such as Glaceau Vitamin Water's energy flavor, contain guarana and regular caffeine, but you have to read the fine print under the Nutrition Facts to know. The front of the bottle focuses on two other ingredients, ginseng and vitamin C, with no mention of the drink's caffeine content.

Electrolytes - These are salts the body loses through sweat. They became a popular addition to beverages when University of Florida researchers developed Gatorade for the dehydrated Florida Gators football team. Electrolytes are great for marathons and high intensity sports, said Nancie Herbold, chairman of the nutrition department at Simmons College. The average person, however, doesn't need to be sipping sodium, magnesium, calcium and potassium salts with their lunch.

Some people also seek electrolyte drinks to treat a hangover, which makes sense to Andover dietitian Rhys Wyman. The sodium and other salts will help you retain fluid, he said, and a drink like Gatorade with a salt and sugar content similar to blood would feel really good. If you have high blood pressure, though, beware of waters that contain sodium.

Vitamins - Vitamin waters do provide a dose of vitamins, but you can get the same effect for less money by taking a vitamin pill with regular water or, even better, through the food you eat, Herbold said. If you're already taking a multivitamin, be careful how much vitamin water you drink. Some people get an upset stomach when they consume too many vitamins.

Oxygen - Consumer reports say there's more oxygen in a breath of air than in a bottle of oxygenated water. A 2003 study in the Journal of the American Medical Association found oxygen water did not improve athletic performance in 11 volunteers. Another study this past March in the International Journal of Sports Medicine found that athletes drinking oxygenated water did not improve their aerobic performance.

Calories - Plain water has no calories. Many bottled "waters" do. Glaceau "fruit water" (which, by the way, contains no fruit) is sweetened with fructose, which gives the drink 50 calories for a 20-ounce bottle. Wild Waters, a colorful fructose-sweetened drink marketed to kids, contains 62.5 calories per 10-ounce bottle.

Some people prefer calories from sugars to calorie-free sweeteners like sucralose, but if you're dieting or your child is drinking 10 of these a day, watch out.

- Julie Kirkwood

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Hydration tips

r Children drink more fluids if their water has a bit of flavor. Instead of buying flavored bottled water with artificial flavors, make your own by adding a splash of fruit juice to refrigerated tap water.

r To make sure that a child gets enough fluids, fill a container of this flavored water, put it in the refrigerator and encourage the child to try to drink down a predetermined amount over the course of the day. This works for elderly people, too.

* Always send a child to day camp with a bottle of water labeled with his or her name. This is better than sending a large container to be shared among children because some kids are germ phobic and won't drink. Separate containers also prevent colds from spreading.

* Coffee and other caffeinated beverages do count toward your overall fluid intake, which is a reversal of the conventional wisdom that diuretics (substances that make you urinate) dehydrate you. The Institute of Medicine reviewed the studies and found that diuretics make people urinate sooner, but over time the person who drank water instead will also lose a lot of that fluid to urination. Whether you drink water or coffee, the hydration is roughly the same in the long run.

* Alcoholic beverages, on the other hand, do cause dehydration. If you are trying to stay hydrated this summer, beer won't help.

Sources: Nancie Herbold, chairman of the nutrition department at Simmons College, and Rhys Wyman, Andover dietitian