July 1 marked enforcement of a building requirement passed last December in Sacramento, California. New construction of 10,000 square feet or more requires a graywater system for subsurface irrigation. At 50,000 square feet, add separate additional piping to "supply water closets and urinals using onsite treated nonpotable graywater."

Expect to see more. Potable water is a geographically nuanced problem and is growing, particularly in relatively dry areas that have seen large influxes of additional population.

The term graywater may be unpalatable, but no one is suggesting that people ingest such water, at last yet. But there are many uses of water that don't require the same quality people would expect from a tap. Graywater is described as "gently used" water from such sources as outflows from sinks, showers, or washing machines. It doesn't include water that has been in significant contact with human waste. So, it's relatively safe to handle and can be used for such things as flushing toilets or watering landscape.