Here in California we have ...

Here in California we have very strict greywater reuse stands where all of it has to be treated for biological contaminants and other constituents of concern including heavy metals, suspended solids, etc. before final end use which at this time is only for non-potable non-crop landscape irrigation. There isn't sufficient studies and data as of yet showing that it's safe to reuse for potable water reuse. In my job as an Environmental Engineer we've only had a couple of greywater treatment system applications for landscape irrigation reuse and even with that the reporting requirements are very strict due to potential for public exposure with the sprinkler system spray. So it really depends on a project by project basis for feasibility of greywater treatment for reuse but 99.9% it has shown to be safe for non- potable landscape irrigation reuse when treated properly.