I have been a resident of the Las Vegas Valley since 1969. Back in those days, the population was small, and we had much more water than we needed. Today, these conditions have change a great deal. Building contractors and realtors want to build, build, build.
Due to changes in our climate, and the extensive population growth along the Colorado River system, our water supply is at risk. Families who have lived in the valley as long as I have, and longer, now have to convert their homes to water-saving systems, cut down trees and pull out grass to be able to afford their water bills.
I live in a two story home in Henderson, built in 1999. I have a new 50-gallon water heater in my garage, and it takes two minutes to get hot water to my second-floor bath. This means two minutes of clean, fresh water down the drain for a shower. Yes, I know that the water runs into the lake, which is then pumped back to be re-treated to be used again. So, we throw clean water out to be treated so it can go back into the lake and then be pumped out of the lake again.
In my investigation, there is no rule in the valley requiring any new home more than one story to have on-demand water heaters on upper floors. We now have three-story homes, which means more wasted water.