Graywater (or greywater) definition?

Graywater is defined as “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.

According to USGBC, in green building projects seeking LEED certification, project teams should comply with the graywater definition established by the authority having jurisdiction in the project area.

Blackwater is wastewater containing urine or fecal matter that should be discharged to the sanitary drainage system of the building or premises in accordance with the International Plumbing Code.

Wastewater from kitchen sinks (sometimes differentiated by the use of a garbage disposal), showers, or bathtubs is considered blackwater under some state or local codes.

Historically it has not been possible to effectively treat graywater and/or black water to become potable water, however that is changing.