Greywater (or grey water, sullage, also spelled gray water in the United States) refers to domestic wastewater generated in households or office buildings from streams without fecal contamination, i.e., all streams except for the wastewater from toilets. Sources of greywater include sinks, showers, baths, washing machines or dishwashers.
Some places collect grey water and use it for flushing toilets. Adding urine to the grey water makes it smelly.
What is “grey water”?
Any water that drains from sinks, showers, or tubs is grey water. Offices, schools, and government buildings here(Canada) do it to save water.
https://en.wikipedia.org/wiki/Greywater