Using Gray Water at Home

Every drop of water counts. Conserve the fresh water supply and save money on your water bill by using gray water for landscape irrigation at your home and following some basic requirements.

What is gray water?

Gray water is wastewater collected separately from sewage flow. Gray water includes water from washing machines (clothes only), bathtubs, showers or sinks.

Gray water may contain fats, oils, grease, hair, lint, soaps, cleansers, fabric softeners and other chemicals. It's important to understand which chemicals go down household drains, as you don't want to use gray water with elevated levels of chlorides, sodium, borax or sulfate that has a high pH, which could be harmful to your plants.

Gray water does not include water from a kitchen sink, dishwasher or toilet. These sources produce "black water," which should not be reused at home because of the high risk of contamination by bacteria, viruses and other pathogens.

Do I need a permit to use gray water at home?

No, as long as you are only using gray water at your private residence, you only need to follow some required best management practices, which were developed to protect public health and the environment.*

Best Management Practices

  • Your gray water must only be used for household gardening, composting or landscape watering at your home, where it cannot be accessible by the public or run off your property.
  • Gray water flow must be less than 400 gallons per day.
  • Gray water may only be used in locations where groundwater is at least 5 feet below the surface throughout the year and cannot be in a floodway (e.g., wash or drainage way).
  • Do not use gray water on any plants that produce food, except trees and shrubs with edible portions that the gray water does not touch.
  • Avoid overwatering and incorporate practices to increase filtration and minimize standing water, such as using mulch cover.
  • Use only flood or drip watering methods. Spraying gray water is prohibited due to the potential for inhalation or drifting off-site.
  • Avoid contact with gray water or soil irrigated with gray water as much as possible.
  • Gray water cannot contain hazardous chemicals such as antifreeze, mothballs or solvents. Do not include wash water from greasy or oily rags in your gray water.
  • Gray water must not contain water used to wash diapers or other infectious garments. This water must be discharged to a residential sewer line.
  • Label pipes carrying gray water under pressure to eliminate confusion between gray water and drinking water pipes.
  • Cover, seal and secure any surge tanks to restrict access by small rodents and to control disease-carrying insects, such as mosquitoes. Also, minimize the time water is held in surge tanks to avoid any unpleasant odors.
  • Should a blockage, backup or overload occur, gray water use must cease until the problem is corrected. The gray water system may include a means of filtration to reduce plugging and extend system lifetime.
  • If you have septic or other on-site wastewater treatment and disposal system for black water, your gray water use must not change the system’s design requirements for capacity and reserve areas. Contact your County for more information about system requirements | Learn More >

Gray water rule | View/Download AAC Title 18, Chapter 9, Article 7 — Part D >

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