The choice to recycle graywater has never been black and white.

The pros and cons of graywater re-use have been debated for decades — California and Florida have championed water reuse for irrigation since the 1980s. An endorsement from the Environmental Protection Agency, and serious issues with droughts and water supplies in some states, have generated increased interest in the process and its potential impact on both energy use and water treatment.

Single-family residences produce a lot of graywater every day. According to the EPA, an average family of four uses 400 gallons of water per day and more than 140,000 gallons annually. The EPA estimates 50% of that could be recycled and reused, reducing water bills and benefitting the environment.

Graywater usually is defined as untreated water from bathtubs, showers, bathroom sinks and washing machines, although specific definitions vary from state to state. Most graywater definitions don’t include: kitchen sinks and dishwashers, because the water contains food waste; and, garage drains and other drainages likely to be contaminated with toxics or hazardous chemicals.

Proponents of graywater recycling list many benefits. On the ecological front, that includes reduced freshwater extraction from rivers and aquifers, less impact from septic tank and treatment plant infrastructure, reduced energy use and chemical pollution from treatment, groundwater recharge, reclamation of nutrients, and greater quality of surface and ground water soil than generated by water treatment processes.

In some jurisdictions, graywater may be used for drip irrigation and toilet flushing. In others graywater can be used only for underground irrigation which requires construction of trenches and subterranean drainage fields that meet restrictions to protect the water table, flood plains, nearby water bodies and land uses. A graywater system typically has a holding tank to regulate flow and most states that permit graywater use require that these tanks be covered or enclosed to prevent tanks from becoming breeding places for mosquitoes or creating other health problems.

Regulatory status

What’s the current regulatory status in the Western states? It varies widely, with some states having established complicated graywater handling codes and others still developing such guidelines.

Alaska: Isolated communities and severe weather conditions present some interesting challenges in the state. Among the research projects into recycling, there is one endeavoring to create a multi-purpose system that can endlessly reuse graywater for many domestic uses. Homebuilders are also talking about incorporating dual plumbing systems into new homes, which can use recycled water for flushing and landscape irrigation as well as heat capture.

Arizona: The Arizona Department of Environmental Quality allows graywater recycling without a permit under limited conditions. As described in the regulations, homeowners may recycle untreated graywater from washing machines, bathroom sinks, bathtubs, and showers, but only if the residence lies outside of an active floodplain. Arizona has separate laws for surface and subsurface graywater use. The state requires a filtration device and a settling tank to separate solids from graywater.

The graywater must originate from the residence and be used only for landscape irrigation. Specifically stated, the graywater from kitchen sinks, dishwashers and toilets is not to be included. Special mechanical considerations include requiring an emergency discharge to the septic or sewer system in case of system failures, and all piping should be of PVC or ABS. Storage containers must be secured with bug- and childproof covers.

California: California’s graywater code is found in Chapter 15 of the California Plumbing Code. Homeowners are allowed to irrigate with untreated water straight from bathroom sinks, washing machines and bathtubs, as long as — among other requirements — the water lines run beneath soil or mulch, so as not to come in contact with people. That rules out using untreated graywater on lawns, which typically need above-ground spray heads or sprinklers. There’s been a push to include graywater reuse systems in new construction, some with the option of integral heat transfer systems to capture energy from exiting lav or shower water.

In recent years, a push has been made in the Golden State to address harvesting graywater in connection with the state’s greenhouse gas reduction goals, as well as serious drought conditions. One study by the University of California at Los Angeles found that if everyone in the Southern part of the state recycled the water that currently goes down drains from their showers and washing machines, there would be enough to satisfy Southern California’s entire outdoor residential water use needs.

Colorado: Single-family and larger recyclers’ allowed uses for graywater are indoor toilet and urinal flushing, and outdoor subsurface irrigation within the property boundary. The Colorado Water Quality Commission Rule 86 describes requirements, prohibitions and standards for the use of graywater for nondrinking water purposes, to encourage the use of graywater, and to protect public health and water quality.

“Graywater” means that portion of wastewater that, before being treated or combined with other wastewater, is collected from fixtures within residential, commercial or industrial buildings, or institutional facilities for the purpose of being put to beneficial uses. Sources of graywater are limited to discharges from bathroom and laundry room sinks, bathtubs, showers, and laundry machines. Graywater does not include the wastewater from toilets, urinals, kitchen sinks, dishwashers or non-laundry utility sinks.

Hawaii: The Aloha State has a long history of rainwater catchment and recycling as well as its aggressive use of solar power. There is currently no formal code regarding graywater recycling, but proposed regulation made it as far as committee level in the state legislature last year.

Idaho: The Gem State has allowed graywater reuse on a case by case basis since at least 2004. Graywater recycling is limited to used water from bathtubs, showers, bathroom wash basins, clothes washing machines, and laundry tubs. Graywater may be used to irrigate lawns or landscape plants, but may not be used to irrigate vegetable gardens. It may not be applied on, nor be allowed to reach, the land surface, which would permit buried drip irrigation systems but not above-ground soaker hoses. The Idaho Board of Environmental Quality has rules for “individual and subsurface sewage disposal systems.”

The State Department of Environmental Quality issues a Technical Guidance Manual which recognizes graywater reuse among alternative systems. Idaho’s seven individual health districts regulate these graywater systems and specialized plumbing designs are reviewed by the Plumbing Bureau of the Division of Building Safety.

Montana: The state allows single-family residences to reuse graywater, and legalizes all systems installed before legislation went into effect in 2007. “Graywater” is defined as wastewater that is collected separately from a sewage flow and that does not contain industrial chemicals, hazardous wastes or wastewater from toilets. A “graywater reuse system” means a plumbing system for a private, single-family residence that collects graywater.

Nevada: Graywater may be used for underground irrigation if approved by the administrative authority. A homeowner must obtain a permit to construct, alter or install a system that uses graywater for authority before such a system may be constructed, altered or installed.

New Mexico: In New Mexico, no permit is required to use a graywater system when the flow is less than 250 gallons per day of private residential graywater originating from a residence for the resident’s household gardening, composting or landscape irrigation. Rules include a covered storage tank, overflow into the sewer system, clear identification of piping as a non-potable conduit, use on the generation site only, application method that minimizes contact with people or domestic pets, and no spraying or discharge into a water course.

Oregon: One of the states with a three-tiered system, Oregon’s Building Codes Division first ruled in 2008 that graywater captured from bathtubs, showers, bathroom sinks and washing machines could be reused for flushing toilets. Later legislation allowed the use of graywater for uses necessary for the survival or well-being of humans, plants and wildlife. Regulations issued in 2012 provide:

•  Tier 1 permits are for single-family residences that generate fewer than 300 gallons per day of Type 1 graywater that will be used only for subsurface irrigation of landscape plants or compost.

•  Tier 2 permits are for all types of buildings using a graywater reuse and disposal system and producing less than 1,200 gallons per day of Type 1 or Type 2 graywater, such as a small apartment building. These permits require the permit applicants to document the system’s design and operation.

•  Tier 3 individual permits are for any graywater system that fails to qualify for Tier 1 or Tier 2, systems presumably designed for larger multifamily residences or commercial buildings.

Texas: Permits are not required for domestic graywater systems that use less than 400 gallons per day, according to the Texas Health & Safety Code – Section 341.039 Graywater Standards. Water must originate from a private residence and be used by the occupants for gardening, composting, landscaping or indoor use, as allowed, including toilet and urinal flushing. Graywater must be collected using a system that may be diverted into a sewage collection or on-site wastewater treatment and disposal system. “Graywater” means wastewater from clothes-washing machines, showers, bathtubs, hand-washing lavatories, and sinks that are not used for disposal of hazardous or toxic ingredients.

Utah: Utah allows only the use of graywater for subsurface drip irrigation. A local health department must clear the design before its installation. For questions regarding the content or application of rules under Title R317, contact the promulgating agency (Environmental Quality, Water Quality). A list of agencies with links to their homepages is available at www.utah.gov/government/agencylist.html.

Washington: Washington has a three-tiered system. All buildings in the state must be connected to an approved public sewer or on-site sewage system and no graywater system can be approved for more than 3,500 gallons per day. Washington State distinguishes between “light graywater” — flows from bathtubs, showers, bathroom sinks, washing machines and laundry-utility sinks — and “dark graywater” — flows from dishwashers, kitchen and non-laundry utility sinks. Washington also limits graywater reuse to subsurface irrigation.

•  Tier 1 permits cover irrigation systems with maximum design flows of 60 gallons per day of light graywater serving a single family residence.

•  Tier 2 permits cover light graywater irrigation systems. Flows must be no more than 300 gallons per day from a single family residence; or no more than 3,500 gallons per day from other types of buildings.

•  Tier 3 permits cover systems of light or dark graywater using a component that treats graywater in preparation for subsurface irrigation.

Wyoming: Wyoming allows surface and subsurface irrigation and other non-specific use of graywater. Graywater reuse systems are permitted on a “permit by rule” system as described in chapter 16 of the State of Wyoming Water and Wastewater Rules. The volume of graywater cannot exceed an average of 2,000 gallons per day.

No application for a permit or fee is required if specific conditions are met, which include: minimal human contact with the graywater, no use of water which may contain toxins or used to wash diapers, for example, unless the graywater system is designed to prevent human or animal contact; and no direct graywater contact with or adverse impact to surface or groundwater. The potable water system must be isolated from the graywater system by the appropriate backflow methods and devices.