Greywater is wastewater generated by household processes such as washing dishes, laundry and bathing. Greywater is distinct from wastewater that has been contaminated with sewage, which is known as blackwater.

There are numerous processes such as using reedbed filter systems, the wetpark systems or the living wall that can be used to clean up greywater.

Recycled greywater from showers and bathtubs can be used for flushing toilets, which saves great amounts of water. Many attempts at this have been made in Germany.

In the water damage restoration industry, grey water is considered to be any water from the exterior of the home, or clean water that has been standing for more than 48 hours.

See also Night Soil