Andrew Knittle of the Daily Oklahoman has an excellent article on water reuse, entitled "Cities looking to increase water reuse." Use of "gray water" is on the rise on the West Coast, but slow to take on in other areas. In the water industry, it is common to hear it said that you can use the effluent from your upstream neighbors, but you can't use your own effluent. Once effluent is treated, though, if treated right, it is as safe as water taken from streams and other surface bodies. And until treatment of effluent is more widely accepted, "gray water" can be used for nonpotable purposes, such as irrigation, as noted in Knittle's article. The obstacles to extensive use of "gray water" are the same -- the cost of infrastructure, and the environmental regulations that otherwise prohibit reuse of effluent. Over time, though, the regulations will soften and the cost of infrastructure will be more in line with the cost of treating and distributing naturally occurring surface water. That is why the West Coast is ahead of the curve on this issue.