How much water is too much, answered (once and for all)

This question has been done to death by now, and yet, almost every day some one asks "how much water is too much water" and the answers vary from a few litters to 20+ litters. So I thought I'd answer it once and for all.

I am not a doctor. But over the last few years I've talked to doctors and surgeons, one after the other because both my parents suffer from kidney problems. For among other reasons, to learn about how to properly manage my water intake. So here's the list:

Water you should drink in 24 hour period:

Children: 1 to 1½ litres.
Adults: 2 litres.
Elderly: 1½ litres.

How much is too much water:

5 litres/day on average over a longer period.

More than 1 litre/h. (always, as our kidneys can not process more no matter how thirsty we are)

21 litres/day.

What counts as water:

Fruits can replace some amount of water. (Cucumbers, tomatoes, strawberries and other fruits with ~95% water content).

Most soups can fill in for some water.

Alcohol DOES NOT count as water. (Alcohol, like beer, lacks salt, iodine, calcium, magnesium and other minerals you'd find in common tap water)

Soda DOES NOT count as water. (I'm not even gonna explain this one)

The symptoms of water intoxication are:

Loss of concentration.
Nausea
Headache
Sluggishness
Loss of balance
And in worst case Cramps.

If you experience one or two of these symptoms and you know you've been drinking a lot of water you should reduce your water intake. If you experience any of the symptoms combined with cramps, you should call a doctor immediately. Serious cases of water intoxication can lead to death.

Other notes:

On hot days or days when for one reason or another you might need to drink more water than usual, you should supplement with additional salt. For instance in food.

Water intoxication is most common among athletes, and especially marathon runners who will drink high amounts of water over short times, diluting the salt in their bodies.

Our body produces 0,5 litters of water (urine) through our metabolism a day, approx. another 1 litter is lost to water vapor in breath, feces and sweat.

Water intoxication or hyponatremia is rare, so don't stress too much about it.

Avoid bottled water, as not only is the plastic worse for the environment and it takes 1500 times more energy to produce than tap water, but some brands filter and cleans the water to such a degree it does not provide you with the needed minerals.

Some sources for further reading (but if you're serious about wanting to know more about the subject, you should contact a physician, don't trust me or the internet):