At home, I tend to use 1 tea bag for a large pot of hot water.

And that gives me 2-3 c. of tea which I do drink it with milk.

When tea is too long in water, it gets bitter. Not recommended.

Loose tea (which i tend to use green tea): I tend to use more tea leaves for a pot.

And for leftover cold tea water, I water plants. They love it.