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Greywater is Great Water for your Plants by Laysan Unger

Posted by: | April 20, 2011 | 2 Comments |

It is safe to assume that most Americans will never drink the water from their toilet – so why does that water need to be potable? The short answer is it doesn’t. For that reason, innovative states are passing laws allowing greywater to be used to flush toilets and irrigate landscaping.[1] Generally, greywater is defined as untreated household washwater that has not come in contact with flushed toilet water (called black water).[2] States that allow greywater reuse are realizing that water that has already been used to wash laundry, dishes, and hands can safely be applied to other narrowly defined household uses as an effective way to reduce overall water consumption. 

            Traditional indoor plumbing creates a significant drain on fresh water resources because potable water is used to meet every need. On average, each Americans use 69 gallons of water a day in their house.[3] Of this daily water use, 48 gallons fit the narrowest definition of reusable greywater (showers, laundry, non-kitchen sinks) while toilet use accounts for 18.5 gallons per person each day.[4] At a very basic level, allowing greywater to be used just to flush toilets in private homes will save almost 20 gallons of freshwater per person daily. This simple reduction can have a considerable impact on the municipal water supply, which is especially important in arid states and those severely affected by drought. 

            Currently 10 states, including Oregon, allow some form of household greywater reuse.[5]  That being said, these states have not adopted a common greywater definition. The various laws draw the line between useable and non-useable greywater by considering the source that produced it. Depending on the source, greywater can contain bacteria, viruses, food particles, soap, chemicals or other additives.[6] The safety of greywater, on a scale of low to high risk, depends on the amount and type of particulate in the water.[7] As a result, states are controlling which particles will be in that greywater by deciding which sources can produce greywater. Through this determination, each state is establishing the balance between health risk and greywater benefit it is willing to tolerate. 

            While state definitions vary on which sources are included, the laws do have similarities. At the least, each definition includes water that has been used for showering and washing clothes, with the exception of laundering cloth diapers.[8] These sources are considered low risk because they contain low levels of bacteria.[9] State laws differ most on whether water from the kitchen sink and dishwasher should considered reusable greywater or unusable blackwater.[10] These sources understandably discharge water containing food particles. Food particles contain higher bacteria levels and food decomposition creates bacteria and pathogens that are considered higher risk.[11] States also differ on where greywater can be applied: indoors, outdoors, or both.[12]  Outdoor uses are lower risk because irrigating with greywater creates a natural filter where the soil removes most of the bacteria and other pathogens from the greywater.[13] Indoor application is higher risk because it has not benefitted from that filtration.[14] On the other hand, indoor use is more beneficial because it uses recycled water for resource intensive tasks (namely, toilet flushing). Finally, states differ on how users can irrigate with greywater, either by allowing surface irrigation or only subterraneous irrigation.[15] Subterraneous irrigation provides all the benefits of soil filtration discussed above, but is more unwieldy to use than surface irrigation.

            In creating greywater laws, states need to strike a balance between the risk and the utility of greywater systems. The risk variation between sources and applications allow states to mix and match to create a greywater system that meets users needs in a safe and practical manner. For example, a law may include kitchen sinks as greywater sources (high risk) but only allow subterranean irrigation (low risk). This combination mitigates a high risk source with a low risk application. States address the decision of how, or if, to combine these sources and applications in both their definition of greywater and the rules governing its use. Even the most restrictive definition of greywater is a strong step for water conservation because any reuse will positively affect the net consumption of water. But legislation that liberally allows the application of greywater is ideal because it encompasses the widest range of users, drives innovation, and allows the user to determine how they can best apply greywater considering the benefits and the drawbacks of the resource. 

            A recent example of expansive greywater legislation is Oregon’s House Bill 2080.[16] This bill allows people to reuse “shower and bath waste water, bathroom sink waste water, kitchen sink waste water, and laundry waste water” for “beneficial uses.”[17] The bill further prescribes that greywater systems are subject to permitting requirements that shall be “minimally burdensome to property owners.”[18] The Oregon Department of Environmental Quality has initiated rulemaking with the advice of an advisory committee pursuant to this bill, and draft rules are currently open for public comment.[19]  Among the proposed rules is a three tiered permitting system.[20]  This tiered system distinguishes between single family systems, systems producing “less than 1,200 gallons per day,” and systems that produce “more than 1,200 gallons per day of greywater or … that treat and disinfect greywater prior to use.”[21] The proposed permit system also includes an exception for greywater systems that only reuse water for flushing toilets or urinals.[22] These in house only uses would not need a permit beyond compliance with building and plumbing codes, which already allow this in home use.[23] 

            Oregon’s expansive bill is a model of sustainable modernization. This law makes greywater systems accessible to everyone from the casual user to the sustainable living innovator. In greywater fitted homes, Oregon’s law both lowers the amount of clean water needed and reduces the amount of discharged water that needs to be disposed of. Greywater systems can divert water that would otherwise go in municipal sewer systems to onsite uses, offering much needed relief to Portland’s overburdened sewage system.[24] Oregon’s greywater bill allows people to strategically consume less water and produce less waste while encouraging innovation and forward thinking action. With this law in place, it is possible for houses to completely disconnect from sewage systems in the future, taking domestic sustainability in an entirely new direction. Greywater use in Oregon is just the beginning of mainstream sustainable innovation in the home. Oregon can be a touchstone for other states considering similar legislation because the law has given Oregonians enough room to both create and refine greywater systems, thus driving innovation in the field. Taking the time to cultivate water conservation techniques now will ensure that faucets will run and toilets will flush for years to come.

[1] The following states currently have legislation allowing greywater reuse: Wyoming , California, Utah, New Mexico, Montana, Arizona, Washington, Massachusetts, Texas, and Oregon. http://deq.state.wy.us/wqd/www/greywater.htm; http://www.deq.state.or.us/wq/reuse/docs/Advisory/GraywaterUseByJurisdiction.pdf; http://www.deq.state.or.us/wq/reuse/graywater.htm.

[2] http://www.greywater.com/

[3] American Water Works Association, http://www.drinktap.org/consumerdnn/Home/WaterInformation/Conservation/WaterUseStatistics/tabid/85/Default.aspx

[4] Id.

[5] Oregon DEQ: Water Quality Water Reuse, http://www.deq.state.or.us/wq/reuse/docs/Advisory/GraywaterUseByJurisdiction.pdf

[6] http://www.doh.wa.gov/ehp/ts/ww/greywaterfact.pdf

[7] http://greywateralliance.org/guidelines-for-gw-reuse.pdf, at 323.

[8] Id.

[9] http://www.doh.wa.gov/ehp/ts/ww/greywater/rule/gw-character.pdf, at 2, 5.

[10] Oregon DEQ: Water Quality Water Reuse, http://www.deq.state.or.us/wq/reuse/docs/Advisory/GraywaterUseByJurisdiction.pdf

[11] http://www.doh.wa.gov/ehp/ts/ww/greywaterfact.pdf, http://greywateraction.org/faqs/greywater-recycling

[12] Oregon DEQ: Water Quality Water Reuse, http://www.deq.state.or.us/wq/reuse/docs/Advisory/GraywaterUseByJurisdiction.pdf

[13] http://www.letsgogreen.com/greywater-recycling.html

[14] http://www.letsgogreen.com/greywater-recycling.html

[15] Oregon DEQ: Water Quality Water Reuse, http://www.deq.state.or.us/wq/reuse/docs/Advisory/GraywaterUseByJurisdiction.pdf

[16] 2009 Oregon Legislative Assembly – Regular Session, http://www.leg.state.or.us/09reg/measpdf/hb2000.dir/hb2080.en.pdf

[17] Id.

[18] Id.

[19] Oregon DEQ: Water Quality – Water Reuse, Public Involvement, http://www.deq.state.or.us/wq/reuse/gwrulemaking.htm.

[20] Oregon DEQ: Greywater FAQ, http://www.deq.state.or.us/wq/reuse/docs/graywater/GraywaterQA.pdf)

[21] Id.

[22] Id.

[23] Id.

[24] Oregon Metro, http://www.metro-region.org/index.cfm/go/by.web/id=15242

under: Natural Resources


  1. By: Nancy on October 2, 2011 at 7:18 am      

    Thanks for the share!

  2. By: Lindsay Tallon on April 24, 2011 at 7:26 pm      

    We have a simple DIY greywater scheme in my house: we have a large bucket sitting in the shower, and we use it to flush the toilet. “If it’s yellow, let it mellow” practice means we don’t usually need to flush our toilet with non-greywater (white water?).