Too much water is very harmful to the body. It dilutes important things like salt which affects the brain. One woman was put on a very low sodium diet and then told to up her water intake - she had an epileptic fit and now has terrible brain damage. Too much can swell the brain and you can literally drown. There is such a thing as water-poisoning.
I was watching "This Morning" a few weeks ago and they were talking about a tennis player (i think) who drank 17 pints of water and died. =/
So i think there is a limit, and like rainbow said, you should only drink about 6 liters a day.
my llc said the whole diluting of salts does not happen with a vlcd only with conventional food!! that because ur only eating 500 cals a day water intake is ok. just dont drink 10 litres in 1 hour!!
i drink mostly 5-6 litres a day and she said this is fine. it all depends on diff peoples bodies!!