Free water?

A neighbor in Cambridge said he'll green up his grass when he turns on his well-water fed irrigation system. Pretty handy for those with a well. But at my house in town, the grass is the color of sunbleached hay. It's a combination of not enough water and the fact that they dropped the sod on top of sand that's packed hard by heavy construction equipment. So basically, the grass is on a skillet and it hasn't got a chance unless we get a ton of rain. I'm planning to put in gutters on one side of my house to drain into a rain barrel so I'll have some water, but I got to thinking--what if I diverted water from my kitchen sink!? Clean enough, I guess. So I shot the question off (worded specifically not to incriminate me) to Bill Dunn, an MPCA wastewater expert. His reply:

Kooks will do almost anything. People on holding tanks are also equally creative. Technically, gray water is sewage and regulated as such. Meaning proper treatment. One has to wonder why they would do it and if the grass would die.

I'll stick with gutters and rain barrels for watering my lawn ... until I think of something else.
-Dan