nonpotable

Nonpotable refers to water that is not suitable for human consumption due to its quality, safety, or regulatory status. It is intended for uses that do not involve drinking or food preparation and is managed under separate standards from potable water.

Common nonpotable sources include captured rainwater intended for irrigation, greywater from baths and laundry (with exceptions for certain sources such as kitchen waste in some jurisdictions), and industrial process water that has been treated to remove contaminants to levels appropriate for its purpose. Nonpotable water may also originate from groundwater or municipal supplies that are treated to meet nonpotable standards. The exact definition and permissible sources vary by country and region.

Nonpotable water systems are designed to avoid cross-connection with the potable supply. They often use dedicated piping and labeling or color-coding, and require backflow prevention devices. Uses are typically restricted to applications such as landscape irrigation, toilet and urinal flushing, cooling in industrial settings, washing, and dust control. Local codes determine which uses are allowed and what treatment is required.

Treatment for nonpotable uses ranges from minimal to more advanced, including sediment filtration, disinfection (such as chlorination or UV), and storage in dedicated tanks. The level of treatment is guided by end-use requirements and regulatory standards and may involve regular testing and maintenance.

Benefits include reduced demand on potable water and lower freshwater costs, while risks involve potential contamination of the potable supply through backflow, improper cross-connection, or poor system maintenance. Effective management relies on compliance with local regulations and proper system design. See also potable water, water reuse, greywater.