I attended a demonstration in Petaluma by Daily Acts, a Sonoma County non-profit, of their graywater system, which was the first permitted residential system in Sonoma County. The workshop was given by Trathen Heckman of Daily Acts and Brock Dolman of the Occidental Arts and Ecology Center Water Institute. Both have been involved with graywater legislation that it is making its way through the state legislature and regulations by Sonoma County.
The simplest graywater system is a laundry to landscape system, which recycles graywater from the washing machine out into the landscape.
This system is easy to install with a few simple parts including a 3 way diverter valve, vacuum breaker and 1″ distribution laterals out into the landscape. In Sonoma County it can all be done with a simple plumbing permit, and without the need for more elaborate design, permitting and plumbing of a more extensive graywater system.
The Daily Acts website has a wealth of resources on graywater and a host of other projects as does the OAEC Water Institute website.
Greywater Guerrillas– has great information, workshops and more
Oasisdesign.net– more graywater design information
Video on Trathen’s Graywater installation in Petaluma: