Grey water is water which has been used in for washing clothes, dishes, or for baths which is not severely contaminated by the bacteria associated with human waste. That water is called black water. It is believed by many people that grey water need not necessarily be mixed with black water and treated as sewage in the same manner. Rather it should be available for irrigation and for other uses, such as flushing toilets.
Health regulations generally require treatment of grey water as sewage.
- "The Dirty Water Underground" article by Gregory Dicum in the New York Times May 31, 2007
- Cleo Woelfle-Erskine, July Oskar Cole, Laura Allen (eds.), illustrated by Annie Danger, Dam Nation:Notes From The Water Underground, Soft Skull Press (April 15, 2007), trade paperback, 300 pages, ISBN 1932-36080-8