How feasible is it to achieve a "zero net water" building, and what does this concept entail?

It's entirely unfeasible; buildings cannot balance water use with savings or onsite generation.

It's only a theoretical concept and not applicable in practical scenarios, as buildings cannot minimize water use or enhance efficiency to a significant extent.

It's challenging but possible; the goal is to balance the total water used with an equivalent amount of savings or on$-$site water generation, minimizing consumption and optimizing efficiency.

It's relatively easy to achieve; buildings can easily balance water use with no need for enhanced efficiency or sustainable practices.