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Gray is the New Green

2012 November 8

By Elisa Hyder

Reduce, reuse and recycle. Did you know this common phrase referring to “green” or environmentally friendly practices applies to water?

Every day, water goes down the drain when taking a shower, washing dishes, or simply washing hands. This “gray water” generated from these domestic activities can be recycled for other uses. Gray water is different from tap water that is safe for drinking (white water), and the water from flushing a toilet (black water). Though not suitable for drinking, Gray water contains considerably lower level of contaminants than black water, making it easier to treat and recycle.

The cleaned gray water can be put back into the home for some domestic activities such as watering plants or suppling toilet water. Reusing just a gallon of gray water a day for a year can save enough water for up to 36 showers! And it reduces the amount of drinking water needing to be treatment for human consumption.

However, gray water is not perfect – definitely not safe to drink – and needs to be handled carefully.

  • Gray water should only be stored for a limited time.  The nutrients and organic matter in gray water start to break down after about 24 hours and can start to emit a foul odor!
  • In some cases, the water should not be used unless it has been treated properly with a cleaning system or filter to prevent contamination. This treating process can be done in a variety of ways, some doable in the home or business place. There are both man-made filters and natural systems that gray water can go through for treatment, like distillation and membrane filtration.
  • Local public health agencies may have requirements to follow when developing and implementing a gray water system, so make sure you check with local jurisdictions to fully understand local requirements if you’re interested in your own system.
  • Check out these helpful FAQs for more on how to use gray water safely.

Learn more about water recycling and reuse here and here!  Interested in even more detailed info?  Check out EPA’s 2012 Guidelines for Water Reuse – Chapter focuses on Individual On-site Reuse Systems and Graywater Reuse.

Some handy homeowners have installed diversion systems to reuse their own gray water, particularly in drought-prone and remote areas.  Water reuse also gets larger buildings points in the LEED certification process; buildings like the Solaire residences in New York City use recycled water from the building for toilet flushing, landscape irrigation and cooling towers.  There are even cases where wastewater treatment plants provide their treated water to local businesses for commercial or industrial use, such as Google’s data center in Douglas County, Georgia (check out the video!), irrigating golf courses, and others from a list of reuse projects in New Jersey.

Have you heard of gray water being reused near where you live?  Would you try this at your house?  Always take care to ensure that you are reusing gray water safely, and check with your local health department if you’re not sure.

Editor's Note: The opinions expressed here are those of the author. They do not reflect EPA policy, endorsement, or action, and EPA does not verify the accuracy or science of the contents of the blog.

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3 Responses leave one →
  1. Robert permalink
    November 14, 2012

    Yeah Elisa, I agree in toto

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  2. Mike permalink*
    December 5, 2012

    Might as well reuse it. After all, but because water is a little bit “tainted” it doesn’t mean that you automatically have to throw it away.

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  3. Mat permalink
    December 12, 2012

    Gray water recycling is going to become more and more important. Some places in California have even banned ion exchange water softeners because the brine wastewater they spit out costs more to recycle for agricultural uses:

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