I recently remodelled both of our bathrooms and I was looking for a way to install an inexpensive greywater system, so I can use my shower water (with a flip of a switch) to irrigate my garden.
I had a hard time finding a turnkey system, but with a little research I came up with a DIY system that uses a pool/spa valve by Jandy and remote controlled actuator by Intermatic to divert water into my garden. A simple switch under my bathroom sink allows me to either run my water to the city drainage system or to a tree in my garden. I uploaded the Youtube video above to show how it all works...
Grey water is reusable water that comes from your shower, bathtub or bathroom sink and can be used for garden irrigation provided that you use biocompatible organic soaps and shampoos like the products from Aubrey Organics. Note that cleaning products that are classified as "biodegradable" are not necessarily good for your plants, the term to look for is "biocompatible". The water can then be used to irrigate your ornamental garden or any edible plants that have above-ground fruits. Using grey water can save you thousands of gallons per year, because you are repurposing water that you have already used once (in the shower, etc.). Saving money (especially as costs will likely go up with ever increasing demand for drinking water) and saving resources is part of our overall approach to steadily turn our regular household into a greener home..
Check out http://www.greywatersystems.org for a full parts list. I'm using a valve that was originally meant for a spa or pool applications.