The scarcity of freshwater resources, exacerbated by climate change, population growth, and increased demand, has become a significant challenge for human societies. Despite the renewable nature of freshwater sources, misuse has led to a decline in underground water reserves, especially in Asia. Only 3% of the world's freshwater is usable, with the majority locked in glaciers and underground. On average, a person uses about 300 liters of water per day, but the hidden consumption can be several times higher. Most of this water is used for washing and personal hygiene, eventually becoming wastewater. Scientists and researchers have proposed various solutions for water recycling and optimization in buildings, with greywater recycling being one of the most effective methods. Greywater, which includes water from baths, dishwashing, and laundry, is easier to recycle and poses less risk due to lower phosphate and nitrogen content. It can also benefit plant growth due to its nutrient content. In rural areas, the use of recyclable water is vital due to the lack of sewage treatment and can significantly reduce reliance on freshwater sources, boosting agriculture and allowing for the replenishment of underground water reserves. However, citizen behavior must change to minimize the ecological impact of greywater recycling, such as reducing chemical detergent use and separating greywater from blackwater before it enters the sewage system. While greywater recycling has many benefits, there are also drawbacks, including the cost of separation systems, a 24-hour storage limit for untreated greywater, citizen indifference due to low urban water prices, government neglect of water shortages in rural areas, lack of public awareness, and inadequate policy-making by Iranian engineering organizations and ministries.