Gray Water

Gray is the New Green

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 2.4.2.1 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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The City of Tucson Goes Gray

On September 23, 2008 I was touring the Upper Santa Cruz River with Amy McCoy of the Sonoran Institute as my watershed tour guide. The trip was awesome; I never knew that the southeast corner of Arizona was so beautiful.

Towards the end of our day trip Amy was anxious to get back to Tucson to attend an important City Council meeting, I didn’t know it until later that it was the vote on the Grey Water Ordinance that Amy was trying to make it to. The Sonoran Institute, using EPA Targeted Watershed Grant funds, helped to put together the ordinances for the City Council vote.

Because there’s so little surface water in the Tucson area, the city’s major water source has always been groundwater. The Grey Water Ordinance is aimed at reducing the use of scarce drinking water to irrigate desert landscapes. The city estimates that 45 percent of water use is for landscaping, and using rainwater and gray water would greatly reduce this.

image of green rain barrell under downspoutThe ordinance requires rainwater harvesting plans and capturing systems for any new commercial building built after June 1, 2010. The Ordinance requires that new homes built after that date be plumbed for gray water irrigation systems. This means having a drain for sinks, showers, bathtubs, and washing machines separate from drains for all other plumbing, to allow for future installation of a gray water system.

A key factor contributing to the success of this ordinance was the involvement from the entire community, from plumbers and landscapers to the Friends of the Santa Cruz River, they all added their support for the ordinances success. In addition to the community support, an EPA grant helped finance some of the work towards creating the ordinance language.

The City of Tucson was selected for a Pacific Southwest Regional Environmental Award and on the day of the awards ceremony, I had no idea who was coming to accept the award, but had heard that Councilman Rodney Glassman was coming. He was the driving force behind the ordinances, but I had no idea what he looked like. Well, Rodney is about 6’8”, and super energetic, really hard to miss. Once we connected it was great to sit and chat with him, he is very passionate about the ordinances, Tucson, and Arizona. Way to go Councilman Rodney Glassman and the City of Tucson!

About the author: Jared Vollmer works in the Watersheds Office at the EPA, Region 9 office. His work is primarily with the State of Arizona, Department of Environmental Quality, on reducing nonpoint source pollution in Arizona’s impaired watersheds. In addition, Jared works directly with the Sonoran Institute, a recipient of EPA’s Targeted Watershed Grant, located in Tucson in the Santa Cruz Watershed.

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.

Please share this post. However, please don't change the title or the content. If you do make changes, don't attribute the edited title or content to EPA or the author.