A: Graywater is untreated wastewater from showers, laundry machines, and bathtubs which has not come into contact with toilet waste. It does not include wastewater from kitchen sinks, photo lab sinks, dishwashers, or laundry water from soiled diapers.
| Graywater Source | Characteristics |
|---|---|
| Automatic clothes washer | Bacteria, viruses, bleach, foam, high pH, hot water, nitrate, oil and grease, oxygen demand, phosphate, salinity, soaps, nitrates and phosphates, sodium, link and other suspended solids, and turbidity |
| Bath tub , shower, and sink | Bacteria, hair, shampoos, hair dyes, toothpaste, body fats, hot water, odor, organic matter, oil and grease, oxygen demand, soaps, lint and other suspended solids, and turbidity |
A:
A: Graywater use is legal provided that it follows the 2010 California Plumbing Code, Chapter 16A Part 1. Graywater is approved for subsurface irrigation systems. Graywater is not approved for root crops or edible portions of food crops. Ponding, spray, or runoff to the storm drain system, to the street or to adjacent lots is prohibited. Graywater is not approved for use with hose bibs, nor any inside water uses such as, but not limited to, toilet flushing. Where graywater systems are installed and a potential for cross connection with the potable water supply exists, a reduced pressure principle backflow prevention device is required downstream of the water meter and prior to any branches from the water main to protect the potable water supply.
A: Graywater is approved for subsurface irrigation for landscapes (point of discharge must be covered by a minimum of 2-inches of soil or mulch).
A: Graywater shall not be used in spray irrigation, allowed to pond or runoff and shall not be discharged directly into or reach any storm sewer system or any surface body of water. Graywater shall not be used to irrigate root crops or edible parts of food crops that touch the soil.
A: Divert graywater to the sewer when graywater contains large amounts of cleaning solvents or bleach, when using hair dye or other harsh chemicals, or for clothes washer waste from washing soiled diapers or greasy clothes. Do not discharge graywater to an already saturated landscape during a heavy rain.
A: Blackwater: wastewater that comes from toilets, kitchen sinks, and dishwashers
Graywater: wastewater that comes from clothes washers, showers, baths, and lavatories
A: Wastewater from these sources is not considered graywater due to its high organic content which may cause oxygen depletion and increased microbial activity and may possibly contain food borne pathogens. (Source: Technical Memorandum on Graywater, Crook & Rimer, Clean Water Coalition and Southern California Water Authority, 2009)
A:
| Rainwater | Graywater | |
|---|---|---|
| Discharge Requirements | Does not need to be discharged within 24 hours, can be stored in a cistern | Must be discharged within 24 hours |
| Location of Discharge | Surface irrigation is okay | Must have 2” of subsurface irrigation or the sewer |
| Cost | Highly variable cost depending on complexity (low for simple (rain barrel), high for complex cisterns/pumps) | Highly variable cost depending on complexity (low for simple [washing machine], high for complex treatment) |
| Water Quality | May be acidic (pollutants from air) | May be basic (shampoos, detergents, etc) |
| Codes | No codes or standards | Regulated by 2010 California Plumbing Code Chapter 16A Part 1 (effective January 1, 2011) |
| Permits | No permits required for gravity based system for single family residential properties. To be exempt from any permit, rain barrels must be installed outside the building. Otherwise consult LADBS and CDPH for permit requirements. | No permit required for Clothes Washer System. Plumbing permit from Los Angeles Department of Building and Safety (LADBS) and California Department of Public Health (CDPH) for Simple and Complex Systems. |
| Usage | Stores water during the rainy season, highly variable supply. | Usage is typically daily |
A: Yes if:
- Your plumbing system is accessible.
- You can answer the Questions Homeowners Need To Answer.
- You are able to maintain the system.
A: The volume of graywater produced varies greatly with the water use habits of the occupants of the home.The California Plumbing Code estimates the volume of graywater produced at 15 gallons per day per person for a clothes washer graywater system. The California Plumbing Code estimates the volume of graywater produced at 25 gallons per day per person for a graywater system collecting the discharge from the showers, bathtubs, and lavatory sinks. A complete system collecting the discharge from all available graywater sources would be expected to generate approximately 40 gallons per day per person.Note that these graywater generation estimates published in the 2010 California Plumbing Code do not account for the 20% reduction of the flow rates of the fixtures mandated by the Los Angeles City Water Efficiency Requirements. This should be taken into consideration when designing a landscape that utilizes graywater for irrigation.
A: To determine estimated savings, please see Graywater Savings.
A: The energy factor for LADWP water (2009-2010) is 1,934 kilowatt per hour (kWh) / acre-feet per year or approximately 6 Watts per gallon. Every gallon of graywater used equates to less potable water that is used for irrigation purposes and less water that is pumped and treated in Los Angeles. A household using 50 gallons per day of graywater reduces California’s energy demand by 108 kWh in a year.
A: The following plants are tolerant of sodium and chloride ions or have been reported to do well under graywater irrigation:
| Agapanthus | Arizona Cypress | Australian Tea Tree | Bermuda Grass |
| Bougainvillea | Carpet Grass | Cottonwood | Evergreen Shrubs |
| Fan and Date Palms | Honeysuckle | Ice Plants | Italian Stone Pine |
| Juniper | Oaks | Oleander | Olive |
| Pfitzer Bush | Purple Hopseed Bush | Many Native Plants | Rose |
| Rosemary | Strawberry Clover |
A: Graywater main contain: Microorganisms (some of which are likely to pathogenic); chemicals that include dissolved salts such as sodium, nitrogen, phosphates, and chloride, and organic chemicals such as oils, fats, milk, soap, and detergents, or particles of dirt, food, lint, sand, etc. Graywater may also contain oils, paints, and solvents from household activities that could have detrimental effects on areas irrigated with the graywater. (Source: NSW Health, 2000)Another issue with graywater is that the volume generated in a home remains relatively consistent throughout the year while the irrigation requirements of the plants vary greatly between the summer and the winter. This creates a potential risk of either providing too much irrigation water or not enough depending on the design of the system. These issues are addressed in professionally designed and installed graywater irrigation systems.
A: When graywater is collected and used in accordance with the California Plumbing Code and when graywater reuse systems are designed, installed, and inspected by qualified professionals, then the risk is minimized, and graywater use is safe. Graywater use represents a potential risk. Graywater is not suitable for consumption. However, it is suitable for subsurface irrigation. Graywater must be handled properly, responsibly and without direct physical contact.
A: Graywater reuse is necessary for the future of California. California’s water resources are limited as underscored by the recent drought. Further shortages would be devastating to the State and would severely impact growth, development and our quality of life. The future of California depends on water: Not only on finding additional resources but on reducing the demand. It has become necessary for the State to develop and exploit more water options to meet both current and future water demand. Graywater is one such additional resource. It provides a means to meet the need through recycling and reuse. Graywater reuse represents a means to achieve a sustainable future for California.
A: Treated graywater is graywater that has been processed through a wastewater treatment system so that the discharge meets certain water quality standards. The purpose of the treatment is to reduce the health risk of the graywater. Reducing the health risk expands the number of its potential uses.
A: Treated graywater for expanded uses such as surface irrigation and toilet flushing is not legal. Before treated graywater systems can be legal for use in California, a number of gaps must first be overcome. These gaps include standards, technology and safety. Currently, there are no standards adopted by the State of California for graywater treatment devices. Standards must be developed for the design, manufacture and operation of these devices. NSF is in development of some standards for treatment devices but they must first be adopted by the State. The technology of the treatment devices exists and is in use in Australia and parts of Europe. It needs to be adapted to the conditions that exist here. Wastewater characteristics vary from region to region. Zoning conditions, lot sizes, soil characteristics, and plumbing materials vary as well. These devices must operate under a range of flow conditions while functioning automatically, reliably, quietly and economically. If they fail, they must do so in such a way that they do not create a safety hazard or a nuisance and can be repaired in a timely manner. The use of treated graywater represents a potential risk that does not exist with potable water. People are accustomed to using drinking quality water for everything. They need to be informed as to the necessity for proper handling and use of graywater as well as the graywater treatment devices to ensure their own safety and that of others.
Glossary of Terms
3-Way Valves: diverts graywater from sewer to distribution plumbing or as a shut-off back to sewer.
Blackwater: toilet water that cannot be reused.
Combined Pump, Surge Tank, and Filter Assembly: a manufactured unit.
Complex System: graywater systems that discharge over 250 gallons per day.
Disposal Field: a landscape designed to absorb the graywater to prevent ponding or run-off.
Distribution System: piping that carries graywater out to the desired landscape for irrigation or disposal.
Filter: used to protect drip irrigation from fine particles and clogging of emitters.
Graywater Sources: washing machine, bath/shower, sink (not kitchen sink).
Holding Tank: temporarily stores graywater until there is sufficient volume to pump.
Irrigation Field & System: the landscape intended to be irrigated by graywater or rainwater, including via a drip irrigation system, mulch basin, or other approved irrigation method.
Labeling: graywater distribution piping system upstream of any connection to an irrigation or disposal field or a distribution valve shall be identified with the words “CAUTION: NONPOTABLE WATER, DO NOT DRINK.” Marking shall be at intervals not to exceed five feet.
Mulch: organic waste material (leaves, prunings, straw, pulled weeds, wood chips, etc). Mulch is permeable and allows rapid infiltration of graywater or rainwater into soil. Mulch Basin: a type of irrigation or disposal field located between or around plants filled with mulch or other approved permeable material of sufficient depth, length, and width to prevent ponding or runoff. A mulch basin may include a basin around a tree, a trough along a row of plants, or other shapes necessary for irrigation or disposal. Mulch basins require periodic replacement and care.
Operation Manual: for instruction on function, maintenance and safety precautions.
Piping: directs the water to your irrigation system.
Ponding: retention of graywater on ground surface for a period of at least 2 hours.
Pump: pressurizes water through distribution system out to landscape (optional– can be gravity fed).
Runoff: graywater that leaves the intended site which may come into contact with the storm drain.
Simple System: a graywater system with discharge of 250 gallons per day or less. Simple systems exceed complexity of clothes washer system and require permits.
Spray: graywater that discharges above surface and up into the air.
Sub-Surface Drip or Irrigation Systems: piping that carries graywater or rainwater out to landscape to be irrigated. Can include drip emitters, mulch basins, etc.
Surge Tank: delays distribution of water by temporarily holding back large drain flows.
Vent: vertical piping that allows sewer gases to safely release to the atmosphere.
If you have additional questions that are not answered here, please feel to contact LADWP’s Environmental Affairs and Sustainability Programs Division at (213) 367-0429 or (213) 367-5095.