“In most places there is a legal requirement to intentionally pollute drinking water with human excrement.” That’s how the Cascadia Green Building Council frames the problem with recycling water. By law and by practice, the region has historically made it illegal, or at least highly impractical, to reuse water, even for uses that obviously don’t require clean drinking water such as flushing the toilet or washing the car. There’s no good reason why we should fill our toilet bowls with clean drinking water rather than lightly used recycled “graywater.”

The Northwest’s water reuse policies are changing, and not a moment too soon. Even in the rainy west side of the region, population growth is pressuring water supplies, just as climate change begins to yield weather mayhem. Water supply problems can be even more intense in the region’s drier places, and in much of the world.

Long ago, health concerns motivated strict no-contact rules for used domestic water: Every ounce of it must leave the area and flow to a waste treatment plant. The laws have scarcely changed until recently. That policy may have made sense when building trades were not very sophisticated in the Northwest, when inspectors were scarce, and when water was bountiful. Now, plumbers and plumbing inspectors are highly professionalized, many builders are creative and green-minded. Plus water is increasingly scarce and expensive.

Fortunately, several jurisdictions in the Northwest are leading the way to legalizing sensible, low-cost water-recycling solutions.

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  • We’ve already discussed the challenges of reusing rainwater. In this post we’ll take a look at another of the best strategies for conserving water, reusing “graywater,” the water left over from showers, baths, sinks, and laundries. In the parlance of water policy, “graywater” is distinct from “blackwater,” which is water contaminated by garbage wastes, soiled diapers, or excrement. In a conventional water system, all the water used in your home is potable water delivered by your local utility. After a single use—whether rinsing your dishes, wetting your toothbrush, or filling your toilet—that water mingles in your sewer pipe, leaves your house, and travels to a treatment plant. Under the current system, the US Geological Survey estimates that the average residents of Idaho, for example, use 189 gallons per day (gpd) of clean water at home, indoors and outdoors. Oregonians and Washingtonians are less thirsty, using 121 and 103 gpd each, respectively, mostly because they devote less to irrigating their lawns and gardens. Similarly, British Columbians use 112 gpd each, on average.

    Whatever the numbers, the current system of water disposal is wasteful, adding unnecessary expenses for utility ratepayers and for governments managing strained treatment systems. It also taxes water supplies. Yet finding ways to reuse graywater—typically by recycling it for non-drinking water purposes such as laundry or gardening—can cut water needs by up to 50 percent in residential and commercial buildings, extending water supplies and saving money. Until recently, however, graywater reuse has either been flatly illegal or required specialized permits that were expensive and complicated enough to render water reuse a nonstarter for households.

    In recent years, each state and province in Cascadia has taken steps to legalize graywater reuse, although each jurisdiction has taken a different approach. In fact, the Northwest is something of a laboratory—a natural experiment that can help us understand what works and what doesn’t.


    In 2008, the Oregon Building Codes Division ruled that graywater captured from bathtubs, showers, bathroom sinks and washing machines could be reused for flushing toilets. But using graywater outdoors required a water quality permit, much like the ones required for municipal wastewater treatment facilities, and high permit fees discouraged outdoor graywater reuse.

    Then, in June 2009, Governor Kulongoski signed legislation allowing the use of graywater for “beneficial purposes,” which under the Clean Water Act means uses necessary for the survival or well-being of humans, plants, and wildlife. With graywater use legal and accessible, approximately half of Oregon’s domestic water could be used for irrigation, potentially saving tens of millions of gallons annually.

    Oregon issued final rules in August 2011, and expects to begin issuing permits for graywater reuse and disposal systems in spring 2012. The rules, based on recommendations of a statewide advisory committee, set out safeguards and limitations on graywater reuse, including strictures that graywater not be used on sites with steep slopes or shallow groundwater, and should not contact the edible portions of plants (which means that graywater can’t be used on root crops such as potatoes or carrots).

    The rules (summarized here) define three graywater types, based on the extent of treatment and allowed uses, as well as a three-tiered approach to permits:

    • 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. These permits may be obtained by registering the system with Oregon’s Department of Environmental Quality and paying a nominal fee to cover administrative costs. (Fees for permits in other tiers are higher, reflecting increasing complexity in the permit review.)
    • 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, or for anyone who voluntarily applies for Tier 3. Because of the volume, potential complexity, disposal design or other conditions, these types of systems, which could include treatment and disinfection are presumably designed for larger multifamily residences or commercial buildings, may require careful review of design, maintenance, and operation.


    Washington also has new graywater rules, which took effect July 31, 2011, the end result of the state legislature in 2006 directing the Department of Health (DOH), in consultation with the Department of Ecology, to develop graywater rules.

    Washington’s new graywater rules mark an important step toward allowing water reuse, but they also contain a number of restrictions. All buildings in the state must be connected to an approved public sewer or on-site sewage system, such as a septic system, and no graywater system can be approved for more than 3,500 gallons per day. (For context, a four person household might consume, on average, around 400 gallons of water per day.) Systems with larger flows would have to be covered by a standard water discharge permit issued by the state’s Department of Ecology.

    Washington 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, prohibits contact with the edible portions of plants, and outlaws its use on unstable land or in environmentally sensitive areas. Local health boards are responsible for issuing permits and establishing fees according to the following parameters:

    • 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. Treatment is required for several conditions, including the use of dark graywater, irrigation of a green roof, or use in an area with high public exposure, such as a playground.


    The Gem State has allowed graywater reuse on a case by case basis since at least 2004, and unlike Oregon and Washington there’s no major initiative afoot to expand graywater applications.

    To maintain water quality and protect public health, the Idaho Board of Environmental Quality has rules for “individual and subsurface sewage disposal systems,” such as septic tanks or other components that are not piped to a central collection system. To assist businesses and residents in meeting those rules, the State Department of Environmental Quality (DEQ) issues a Technical Guidance Manual (see chapter 4 especially, for diagrams of interesting graywater system designs), 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.

    In Idaho, graywater recycling is limited to used water from bathtubs, showers, bathroom wash basins, clothes washing machines, and laundry tubs; it does not include wastewater from kitchen sinks nor any water that has touched a toilet. 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.

    British Columbia

    Using reclaimed water, including graywater, in British Columbia requires overcoming a number of hurdles, such as producing an environmental impact statement for systems with flows of 27,000 liters (7,128 gallons) or more per day—a system that might serve roughly 70 people—or winning approval from a local health authority for systems with smaller flows. As a result, officials have approved few pilot or demonstration graywater reuse projects, but wider use remains limited.

    In 2009, Meaghan Hennessy, a student at Simon Fraser University, completed her Master’s Thesis in Resource Management by evaluating “blockages,” or regulatory, technical, and economic barriers to the residential reuse of graywater in the Greater Vancouver Regional District. (The full thesis is here; the findings are in Chapter 5.) Her research was informed by interviews with 27 stakeholders, including 4 regulators. While the author cautions that her conclusions are limited to the stakeholders she interviewed, she did find common themes and shared opinions. The stakeholders most often identified vagueness and lack of guidance as regulatory barriers to residential reuse, although regulators tended to view the current rules as necessary to protect public health.

    At the moment, there appears to be little movement in BC toward greater legalization of residential graywater systems. Further progress in the province may rely on the success of demonstration projects or perhaps importing some of the new policies developed in nearby places like Oregon and Washington.

    What’s next?

    Reusing graywater holds enormous potential, but it’s only the beginning of what the Northwest may ultimately be able to accomplish for water conservation under more permissive rules. Some advocates argue that composting toilets, onsite sewage treatment, or large-scale rainwater capture and reuse hold even greater promise. For example, Victoria’s Dockside Green neighborhood and the Bullitt Foundation’s new Cascadia Center in Seattle are pointing the way toward more self-contained water systems. They will each pipe all wastewater to an on-site treatment plant.

    We don’t yet know if the region is striking the right balance with water recycling, or if states and provinces should go further. At the moment, then, the Northwest’s greatest opportunity is probably learning. With new policies in place in Washington and Oregon, and new thinking emerging in Idaho and BC as well, we will begin to see how water reuse is best legalized. Carefully evaluating the experiments now underway should reveal the safest, cheapest, and smartest ways to conserve water.

    Will Northwest graywater users run afoul of a “Murphy’s Law” syndrome that concerns some BC regulators, in which inexperienced homeowners improperly manage their systems and create potential health hazards? Will the region’s consumers and builders take up water recycling in earnest under the newly reasonable rules, or will graywater reuse remain on the fringe? Or will graywater reuse soon become as commonplace and cost-effective as low-flow toilets and faucet aerators?


    Note: For simplicity and ease of reading, we’ve used the spelling “graywater” throughout this blog post. It’s the spelling consistent with Oregon’s usage and it is, we believe, the most common practice in the field. Note that Washington and British Columbia use the variant spelling “greywater,” while Idaho calls it “gray water.”

     John Abbotts is a former Sightline research consultant and a long-time friend of Sightline.