What are the considerations of using harvested greywater for a building?
• An efficient greywater system first requires a steady source of greywater. The most abundant source is showers in buildings with full time residents – dormitories, hotels, schools, etc. Restaurants with heavy dishwashing or clothes washing use may also produce suitable quantities to support greywater harvesting. Office buildings generally do not produce enough usable greywater to warrant the cost of a system. • When there is an abundant supply of greywater, it can be a more reliable source of water for flushing toilets than rainwater. The amount of shower and sink usage generally ties to the amount of toilet use in a building, so there is almost always a balance in supply and demand for greywater. • Greywater harvesting requires additional treatment versus rainwater. This is due to the heavier load of soaps and organic particles that are carried in greywater. The additional filtering and sterilization requirements can add 50% to the cost of a system vs. rainwater harvesting systems.
