Human liquid waste is divided into two categories based on contamination level. Greywater is waste water from sinks, showers, bathtubs, and laundry machines — water that has been used but has not come into contact with toilet waste. It is relatively low in pathogens but high in nutrients, soaps, and suspended organic matter. Greywater makes up the majority of a household’s waste water by volume (typically 65 to 75 percent).

Blackwater is waste water from toilets, which contains fecal matter, pathogens, and concentrated nutrients. Blackwater requires more intensive treatment than greywater and must be handled with greater care during construction and maintenance. In a Pangea building, greywater and blackwater are managed through separate but connected treatment systems.