Glossary | U.S. Green Building Council
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“untreated household waste water which has not come into contact with toilet waste. Graywater includes used water from bathtubs, showers, bathroom wash basins, and water from clothes-washers and laundry tubs. It must not include waste water from kitchen sinks or dishwashers” (Uniform Plumbing Code, Appendix G, Gray Water Systems for Single-Family Dwellings); “waste water discharged from lavatories, bathtubs, showers, clothes washers and laundry sinks” (International Plumbing Code, Appendix C, Gray Water Recycling Systems). Some states and local authorities allow kitchen sink wastewater to be included in graywater. Other differences can likely be found in state and local codes. Project teams should comply with the graywater definition established by the authority having jurisdiction in the project area.