Yes you can. You need to make sure that you spread it out through the course of the day. There have been cases of people dying from drinking 5 litres in an hour etc. Be sensible, and you will be fine. I don't know if there is a definitive answer to your question about an exact amount but I am sure someone will have some input.
Oh god its defiently not that much in such a short time. But i think i might drink 2 to 3 litres during the day. But iv always drunk quite a lot even before i started the cwp!!