The water crisis is causing dramatic changes in the building industry. Contractors and individuals are putting in showers instead of bathtubs. The number of bathtubs is falling and the number of showers is rising, as is awareness of environmental issues among contractors. There are valves and flow regulators for almost all products.
There are also greywater-to-irrigation systems. This is taking up steam. I saw it coming but had no time (or no energy) to promote myself in this field.