Here's a more pressing and actual problem for many US states and cities. In multi-unit condo buildings, the pipes and systems were designed at a time when wat

Here's a more pressing and actual problem for many US states and cities. In multi-unit condo buildings, the pipes and systems were designed at a time when water was so cheap and abundant that it's not individually metered. You pay through your HOA/condo fees as a group. You just live with the fact that a family of 4 likely uses much more than a single person because it's "pennies" difference if you billed it properly. (Admittedly there is both the cost of the water, and the natural gas to heat it, but same principle) But in the more recent climate of water scarcity/energy waste awareness (and costs of energy rising), it would be a kind of holy grail to find a way to install meters for individual units at a cost-effective price of the hardware and labor needed to do such a thing. It would lead to much conservation I think. But there are so many problems in trying to do this. Even starting with the design of buildings being unsuited to do this -- for example tall apartment buildings, your pipes tend to be run as "stacks" so that the bathroom located in the same position on each floor can have piping run vertically. It's not like each apartment is self contained and has a single inlet/outlet for water to place a meter. Sometimes I think about whether you could, if clever enough, derive the usage of a single unit by measuring at the row/column of each floor/stack like addressing pixels... It's a problem, when things were designed for a time when it was much cheaper.