We looked into grey=water recycling for our house remodel. The best sources to "pipe back" were laundry (non-existent in our little trailers) and shower water.... I'd add bathroom sink, as the biggest contaminant would be body dirt and toothpaste... Still, we needed filters & sanitizer to make it work in a stick house, as we would, actually, in a trailer. I'm still on the fence on the expense vs. gain. We may just look at double function flush toilets, instead. We're used to conserving water anyway....
I wouldn't want to deal with kitchen waste coming back thru the (normally) santiary pex pipe to the toilet... too many problems. You'd be looking at a lot of plumbing to isolate grey to the toilet, only, supplemented by fresh when needed. (see this link
http://www.treehugger.com/files/2006...saver_tech.php ..designed for homes, which fills a tank from grey shower or sink, and adds unused fresh when needed only...)
Gina's drain it off into a jug method is easier, and more sanitary than trying to recycle all the grey.