Interestingly, growing up, I thought a second set of pipes for "non-potable" or reclaimed water was standard. Where I grew up in Florida, every lawn was watered with reclaimed water. According to their website[1], Florida is currently reusing 660 million gallons of water per day. Really makes me wonder why states that are in apparent perpetual drought condition haven't adopted similar techniques.

[1] http://www.dep.state.fl.us/water/reuse/