Book 30, Question 90
What is graywater, and can it be reused?
Graywater is gently used household water from sinks, showers, and washing machines.
It is not water from toilets, which is much dirtier. Graywater still has soap and some germs, so it is never for drinking. In some places, rules allow it to be reused to flush toilets or to water ornamental plants. Graywater can help save fresh water, but only when a plumber and local rules are followed.