Too much water?

I drink from 4 to 6.4 liters a day. I don't just chug water down on itself, I drink green tea cos I love tea. And I drink slowly, around one mug a hour. I feel great.

You could get water poisoning if you consume huge amount of water, like 2 liters, maybe even more, in very short time, like in 1 hour or something. And even then you would need to do it multiple times a day to feel any significantly noticeable symptoms because I have drunk 2 liters in 5 min once just for contest with my friends and I was completely fine.

If you spread it all through the day it is completely safe. In hot climates where you sweat a lot drinking 6 liters a day might even be recommended norm, your body is perfectly capable processing it and you will just pee out all it does not need and not store it and get poisoned, unless you drink huge amounts in one sitting and overwork your kidneys.

The recommended rule used to be 8 cups of water a day minimum for everybody, which is also what My Fitness Pal Recommends, but that is now outdated science. Now the general rule is to drink between half an ounce and an ounce of water for each pound of your weigh to be fully hydrated, because how much water we need depends on many things such as our weight, activity level, how hot climate we live in, diet, etc. So if you weight 170 pounds it's between 85 (2.5 liters) and 170 (5 liters) ounces a day. For hot climates probably at the upper limit and for not so sweaty places lower limit.

You can drink too much, especially if too much at once but rarely would someone reach that point. I aim for 9-10 glasses a day (I weigh about 168 and am relatively active). Most people don't drink enough and aren't aware of that. I think you're doing fine with your amount, not so sure about the amount of tea though.....I would consider cutting that back some unless you're doing fine with eating a healthy diet with enough fruits and veggies.