I drink between 4 and 6 litres a day and have mostly tetra's. I kind of use the rule of thumb if I'm thirsty I drink if I'm not I don't, but I have alway's drunk alot
I just fill the fridge with loads of water bottles and somehow manage to get through them..I'm much more of a fizzy drinks person..hence the need to diet lol
I alwasy rink about 3.5 litres , but remember that you can drink too much too ... much over 4 / 5 litres is not good for your kidneys , if you use tetras you need to make sure you have at least 3 litres