Tetras - how much water do I need to drink?

Hi
I am starting tomorrow. I am super fussy, so to ensure I don't give myself any excuses, I have bought only tetras for my first week.
2years ago when I first tried CD, I gave up as although I didn't cheat, I started putting on weight, as U wasn't drinking enough water.
Has anyone else had a tetra-heavy menu?
How much water do you think I need to set myself as my minimum target each day?
Thanks

they say an extra glass of water for every tetra or bar so I would say at least 3 litres , I drink between 3.5 and 4 a day pretty easily with the orange flavour

Thanks. I'll aim for four....and as ling as I hit three I should still be ok!