you asked about the correlation between water molecules in a liter and number of liters in the ocean, hence my metaphor. the rest has been answered elsewhere in the thread.

water filtration plants don't take water from the ocean nor does your waste empty into the ocean so the finite number of water molecules cycling around in the clean water you and i drink is much smaller than the ocean. he's using the ocean as an example of the largest possible body of water and even then, you're likely to get the same atoms every so often. so when you scale water filtration back to the state or county level, include water tables, local sources such as wells or reservoirs... the odds increase even more.

ps i don't understand why you need to give me attitude for answering your question.