Colorado’s Water Plan (CWCB, 2015) predicts that Colorado will be faced with a significant water supply shortfall within the next few decades and describes strategies to eliminate the shortfall by 2030. One strategy that the plan identifies is reuse of graywater. When used for drip irrigation of non-food plants and for flushing toilets, graywater can help save Colorado’s limited water supplies.
Graywater is wastewater that originates from a clothes washer, bathtub, shower, or bathroom sink and can be used in your home for certain types of irrigation or for flushing toilets. Graywater is different from “black water,” which is wastewater from toilets, kitchen sinks and dishwashers. Black water is not safe for reuse in the home because of the high risk of contamination by bacteria, viruses and other pathogens.
Graywater sources include water discharged from:
Graywater does not include water discharged from:
Every time we shower or wash clothes, we make graywater that is usually disposed of. Residents can lower their water bills and conserve a valuable resource by making their systems compatible with graywater reuse. Graywater can perform two important, water-intensive functions: landscape irrigation and toilet flushing. A study by Greywater Action on residential graywater systems found that the average household saved over 14,000 gallons of water per year by installing graywater filtration systems in their homes without negatively affecting soil or plant health.
You can learn more about graywater and graywater systems at Graywater Central at Oasis.com or at Graywater Action. Note that some of the uses and systems described on these web pages are not allowed in Colorado. Detailed information on allowable graywater systems in Colorado can be found on the State of Colorado’s Graywater web page.
Full design requirements for Denver: Rules and Regulations Governing Graywater Treatment Works.
Visit Development Services’ web page for information on obtaining permits for installation of a graywater system.
A laundry to landscape graywater system is a simple system that distributes greywater from a laundry machine to multiple plants or a mulch basin. Laundry to landscape systems are relatively inexpensive and easy to install. The laundry machine’s internal pump pressurizes the greywater, so this system can irrigate plants across a flat yard.
Laundry-to-landscape system. Image credit: CleanWaterComponents
If you are thinking about installing a laundry to landsacpe graywater system, you must comply with the following requirements:
Allowed Uses and Systems
If you plan to use graywater from a laundry to landscape system for irrigation, you should be aware that laundry detergents may contain chemicals that can be harmful to your soil and plants. Here are some things you can do to help improve graywater quality and ensure your soil and plants remain healthy and hardy:
Colorado Graywater. Laundry to Landscape Best Management Practices. 1 page.
University of California Vegetable Research and Information Center. Using Household Waste Water on Plants. Universitry of California, Division of Agricultural Sciences, Leaflet, 2968, 2 pages. Available at: http://vric.ucdavis.edu/pdf/fertilization_Householdwastewater.pdf
Committee on the Beneficial Use of Graywater and Stormwater (2016). Using Graywater and Stormwater to Enhance Local Water Supplies: An Assessment of Risks, Costs, and Benefits. Water Science and Technology Board; Division on Earth and Life Studies; National Academies of Sciences, Engineering, and Medicine. The National Academies Press, 224 pages. Available at: http://www.nap.edu/21866.
For more information on Graywater, its potential uses and installing graywater systems, contact the following City & County of Denver departments:
Denver Department of Environmental Health, Environmental Quality Division
Department of Community Planning and Development, Neighborhood and Inspection Services Division