I drink 4-5L of water a day (I exercise in an aircondit gym, only drink there when I get thirsty, live in a city with alot of pollution and it makes me thirsty, then I go home and try not to binge...so I drink more water) been drinking my 4-5L of water a day for quite a few years now. Am probably over hydrated- notice the dizzy spells, fatigue and odema if I drink even a glass more then the above and you know what? I have not lost weight for about 5 years.
Water will not make you lose weight, dropping calories is the only way. If you drink water instead of eating then you will lose weight, but please don't be under the assumption that water does this, its calorie reduction simple as.