Dehydration can cause serious damage
UK experts say research which finds drinking lots of water does little to improve health should not discourage people from topping up regularly.
A scientific review by the University of Pennsylvania said some people, such as athletes, may need to drink a lot.
But they found little evidence that flushing out toxins through drinking copious amounts improved health.
However, the Food Standards Agency is sticking to its recommendation to drink six to eight glasses of fluid a day.
The body's natural systems normally keep us topped up with water by making us feel thirsty, but various arguments are used to justify drinking extra.
It has been claimed that it can help remove toxic chemicals from the body, stop headaches, make you eat less, and even keep your skin healthier.
Dr Dan Negoianu, and Dr Stanley Goldfarb, writing the the Journal of the American Society of Nephrology, say that while dehydration can be harmful, there is scant evidence that large amounts of water offer any benefits.
In fact, they said, there was no evidence supporting the standard US recommendation of "8x8" - eight glasses, each containing eight ounces of water (a total of 1.8litres), a day.
They wrote: "There is no clear evidence of benefit from drinking increased amounts of water.
"Although we wish we could demolish all of the urban myths found on the Internet regarding the benefits of supplemental water ingestion, we concede there is also no clear evidence of lack of benefit.
"In fact, there is simply a lack of evidence in general."
Looking at other scientific papers revealed that while drinking more water did effect the rate at which various substances were cleared by the kidney, there was no suggestion that this led to any actual health benefits.
While one small trial found that drinking more water appeared to lead to fewer headaches, they said these results were not statistically significant.
And while dehydration can change the appearance of skin, there were no studies which suggested any clinical benefit to skin tone from drinking more.
In the UK, recommendations vary, with the Food Standards Agency's "Eatwell" website advising the public to drink six to eight small glasses of fluid a day - equivalent to 1.2 litres.
A spokesman said this estimate was based purely on studies of the fluid lost each day by the body, rather than any purported health benefits.
"In temperate climates, such as the UK, the government advises that six to eightglasses of water - about 1.2 litres - or other fluids should be consumed every day to prevent dehydration.
"The average 70kg man has a total daily water excretion of 2.5 litres - 1.3 litres is received from ingested food and metabolic activity with the remaining 1.2 litres coming from drinking."
The British Nutrition Foundation opted for slightly more, encouraging people to take between 1.5 and two litres.
However, a spokesman said: "I'm not sure how much science there is behind any recommendation that people drink more than this, unless you are doing a lot of physical activity or sweating a lot."