I drink a ton of tea (up to 4 litre a day, no milk or sugar; usually black, sometimes green), but nevertheless when I go a day without, or drink much less of it

I drink a ton of tea (up to 4 litre a day, no milk or sugar; usually black, sometimes green), but nevertheless when I go a day without, or drink much less of it, I suffer no real side effects and can function adequately. I'm still not sure whether this is healthy for me, though.