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Greywater Studies

This page includes current studies on greywater. We believe it is important to look at potential risks associated with greywater in a broader context. Risks associated with an insecure water future, climate change, and sewer overflows are all risks that could be alleviated by widespread use of greywater.

Many authorities cite health concerns as reason for restrictive codes. To understand more about these potential health concerns read Art Ludwig's explanation of fecal coliform bacteria counts. Although studies have found fecal coliform indicator bacteria in greywater, there has been no documented case of illness associated with greywater. There is also uncertainty whether the indicator bacteria found in greywater represent the true quantities of potentially dangerous bacteria. A report from the Water, Environment, Research Foundation concludes:

               "But there is controversy regarding whether the indicator organism counts are an accurate indicator of the actual health threat posed to the homeowner who comes into direct contact with graywater because fecal coliform concentrations have been observed to multiply in graywater, whereas pathogens have never been observed to grow in graywater and die off
rapidly. Therefore, a high graywater fecal coliform count may not indicate the same level of pathogen exposure risk as the same fecal coliform count found in treated wastewater." (5-4 Long Term Affects of Landscape Irrigation Using Household Graywater)

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