Depends on who you ask. I'm a believer that 'the more you drink the more you shrink' is NOT true. Yet a lot of people claim it is true. For me personally I retain water if I drink too much. Plus I feel sick if I drink too much. But everyone's different and everyone has their limits.
So long as you get the minimum of 2.25l in addition to that you have in your packs you will be fine. Drinking more water may help minimize the effects of ketosis, and if you don't drink enough can cause retention, but like Debz, I don't believe that drinking more will make you lose more!