What about a diverter and off/on valve in front of a spigot connected to separate water lines from sink, toilet, etc...
for urban homes for access to both city lines and grey
water access. Has anyone done this?
thanks

Try reading from these sites. Usually I can find the answer to water and gray water questions at one of these places:

http://greywateraction.org/

http://www.harvestingrainwater.com/

http://www.oasisdesign.net/index.htm

Look at the links or section of "resources" at each site and it will take you to more good information. I like to read from the WHO site too and they link to all sorts of projects.