Their sizes and quantity they hold vary. We need to know which one specifically to answer as to capacity.
There are many sizes of teapot. I could not even guess at the average size.
40 gallons is 320 pints.
4
Four cups.
Purchase 2 quarts. It will take 3 to 3 1/2 pints to fill it.
8 fluid ounces = 1/2 pint
It is 60 pints per minutes.
2.5 pints
It takes 2 pints to make a quart.
7 pints
It should take 3 1/2 pints to fill it.
4 pints many or 2 qts for many. You just fill to bottom of fill hole when cover replaced. The tricky part is getting a good seal on the cover.
3 quarts = 5 UK pints = 6 US pints