Grey water (also spelled gray water) is all wastewater generated in office buildings or households from streams without fecal contamination. Grey water is generally defined as wastewater from baths, showers, basins, and washing machines. Compared to municipal wastewater treatment, Grey water treatment is easier as it generates a large interest in its reuse and recycling. Generally, recycling and re-use are done for toilet flushing, irrigation, and other non-potable uses.
A crucial part of the sustainable management of water resources is reusing wastewater. For the tourist and arid areas in which the biggest water demand is usually in the dry period, Grey water can be an important alternative water source.