The plastic diverter valves above are the best solution currently available for greywater diversion in 1.5 or 2" pipe. However, they are made of PVC, a bad plastic.
Before clicking the "buy" button, make sure your system is designed to use as little resources as possible in its use and maintenance, including using as little plastic, as little bad plastic, and as few valves as possible. The typical system uses at most three of these valves, one for the kitchen sink (yes, this this is legal only in Arizona so far, but the rules will catch up elsewhere before the house falls down), and one for the rest of the plumbing, and a one-inch brass valve from the laundry. Why are we offering these if they are made of bad plastic? Well, they are the least of evils in many contexts that have conventional plumbing (which, in the West, is actually ABS, slightly better than PVC). It is possible to make greywater valves of a better material (and a better design). If you or someone you know has a plastics manufacturing plant, please contact us for a design for better valves. The minute there is a more ecological valve, we'll drop these. Also, consider that the whole idea of diverting greywater "elsewhere" is suspect. If it is too toxic to put on your garden, where exactly is it OK to put it? A more fundamental solution is to not buy anything that can't go on the garden, then put it all on the garden full time; no diverter valves.