A gallon of water weighs ten pounds, outside of the USA. 16 fluid ounces in a pint, is a measure of volume, not a measure of weight, which is an avoirdupois ounce (dry weight). A fluid ounce is equivalent to 1.0425 av. ounces. A gallon of water weighs 8.34 pounds.
There is the same amount of water on Earth as there was when the Earth was formed. The water from your faucet could contain molecules that dinosaurs drank.
Nearly 97% of the world’s water is salty or otherwise undrinkable.