Greywater, which is wastewater from activities like bathing and laundry, is being reused after treatment. Recent global developments focus on reusing greywater to create water smart cities. Greywater varies in quantity and quality depending on the country. This article discusses common greywater reuse practices, quality and quantity of greywater, calculating greywater footprint, codes, integrating with rainwater or stormwater, design considerations, management strategies, and example problems.