Gray water is such a simple idea, but it is expensive to implement the infrastructure on a mass scale - particularly in the suburbs. There is however, more interest in the idea thanks to an increased knowledge about how important water is. Californians are now looking more at gray water - and in the USA California tends to set trends for the rest of the states.

The systems — which use water from sinks, tubs and washing machines to irrigate home landscaping — are touted as a way to keep lawns green and flowers blooming without abusing a scarce resource or inflating water bills.
Greywater Guerrillas launched its first jerry-rigged experiments with gray water in 1999, when the original guerrillas were trying to reduce the water bill for their house of six roommates. The systems and devices have become much more sophisticated since then, said Laura Allen, an educator with Greywater Guerrillas.
Gray water systems channel the used household water (though not from toilets) to irrigation ducts 9 inches below the surface of a home’s lawn or garden.
Advocates say it’s a practical use of water that otherwise would go into the sewer system, and therefore an expedient means of conservation. And conservation is important as water becomes an increasingly valued resource, proponents say.
“Our water bill is going to be like our oil bill in the future,” said John Russell, a landscape designer who heads WaterSprout, an Oakland company that specializes in residential and commercial irrigation, including gray water systems.

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