I think having about 3 litres of water a day gives good results.
I know you're meant to drink a little over 2 litres to make up the water we would usually get from eating normally and then maybe drink alittle extra to help with losses.
I have read a few threads that state that the amount of water you drink has no effect on losses but i'd just expereimnt with it. Maybe drink 2 litres for one week and then 3 litres the next and see if it affects you losses.
xx