You can drink too much water, but it's difficult to do. A healthy person's kidneys usually remove excess water from the blood pretty quickly. A healthy intake for a woman is about 2.7 liters (91 ounces)per day, with about a fifth of that coming from food. You can usually drink more than that without any real problems other than the need to visit the rest room. If you drink water frequently throughout the day,your body will just make more dilute urine. So unless you are drinking WAY more than normal (like more than two gallons in under an hour), youprobably don't need to worry about it.

One situation where healthy people have died from drinking too muchwater is in marathon races. When you exercise, your kidneys don't workas hard. Blood is sent to the heart and other muscles and away from thekidneys, digestive system, and other areas. People who are fairly slowrunners may be running for over four hours, and drinking a lot of waterand sports drinks. Meanwhile, their kidneys are not removing the waterfrom the blood, so their blood volume and pressure go up. This causessome of the water in the blood to leak into the lungs.

Another problem is that they mess up their balance of salt and water.The heart works because of the levels of "electrolytes," including thesodium in salt, so an irregular heartbeat is one symptom ofover-hydration. Messing up the salt-water balance also causes theircells to swell up. Swollen brain cells can cause seizures and behaviorthat makes a person look drunk. This is called "water intoxication."It can lead to death.

Sometimes babies can have problems if they drink too much water, like iftheir formula has been watered down too much. The kidneys of babies arenot yet as efficient as they will be.

What do you think will happen if you don't drink enough water? Wouldsalt help a person who drank too much water, or would it hurt them?

Yes, it can be deadly to drink too much water. The question of just how that happens is answered here:

Yes, you can drink too much water. It will mess with the electrolytes in your blood and make your body less likely to work properly. This is similar to when you are dehydrated which is why you drink electrolyte fluid(Gatorade, etc) to replace electrolytes lost through sweating. But when you drink too much water the electrolytes are diluted and have difficulty reaching the cells.

You'll die. Yes, even water is poisonous if you have too much of it!

The fluids in your body have a certain concentration of dissolved material, nutrients, oxygen, salt, and a bunch of other things. If you have too little water, then the concentrations get too high and your body chemicals won't work right because they get jammed by all of the extraneous stuff. If you have too much water, however, they won't be able to find what they need in all of this excess fluid.

It is dangerous to drink too much pure water. Water intoxication or "water poisoning" occurs when people drink so much water that the body loses the balance of electrolytes. The body needs a certain amount of sodium and calcium in the bloodstream for proper operation of the brain and muscles. If you dilute the blood too much, the brain and muscles can fail, resulting in coma or heart attack and death. Several people have died from water-drinking contests. Normally this is very difficult to do: an adult usually has to drink 1-2 gallons of pure water for symptoms to occur. But children and especially infants are more susceptible due to their smaller bodies. Water poisoning is easy to prevent: simply eat or drink something with good electrolyte balance, like a banana and a sip of a sports drink. Water poisoning can also happen to people doing extreme exercise or taking drugs (whether legal medications or illegal drugs like ecstasy) which make them very active or thirsty, if they drink only water with no electrolytes.