Gray water is one of these things that takes real commitment. It is not an easy retrofit like solar pannels, once those are installed they pretty much run themselves. But a water catchement system is a lifestyle change. One book I read back a while ago, Design for Water by Heather Kinkade-Levario, is a great starting point. And there are devices out there that you can use for a retrofit if you are going to go this route…I have a few hogs I bought on sale that I am going to hook up soon, they are pretty cool and if you have a way to get them installed I recommend them. The Chronicle has a good piece today on Graywater as wel, and while it might not be at the top of your list when it comes to your next remodel, maybe you can think about ways to intgrate it.