Gray Water: the New Green

By Doug Pushard

Gray water has been around for decades. Gray water is the recycling and reuse of wastewater from the shower, tub, clothes washer, bathroom sinks and floor drains for onsite use. This volume of water can be over 50 percent of the water consumed inside a typical home and almost a third of the total overall. For a single-family home in the Santa Fe area, it is approximately 56 gallons a day, 1,700 gallons a month and over 20,000 gallons a year!

Gray water, greywater or grey water are all the same. Although we can’t agree on what we call it, both the model plumbing codes—the International Plumbing Code (IPC) and the Uniform Plumbing Code (UPC)—now have sections dedicated to detailing how these systems should be implemented.  

Doug Pushard
Doug Pushard

These new codes have enabled states and local jurisdictions to adopt regulations allowing gray water systems to be built. Prior to these codes, some states (e.g.,., Arizona and New Mexico) led in this area by adopting statewide codes to allow these systems at a residential level (i.e., the discharge of less than 250 gallons per day). Some states struggle with the concept of allowing gray water systems (e.g., Texas and California), permitting it in some jurisdictions and not others or allowing it but making it very difficult to get a permit, while others states are still lagging in this area of water reuse (e.g., Colorado).  

While city water is a good source of drinking water, it should be secondary when it comes to landscape water use. Below is a summary of the characteristics of each, comparing city drinking water with gray water:

Gray water is a great source of irrigation water, which in many locations in the Southwest is 30–50 percent of the overall water use. Gray water will usually contain sodium, calcium, magnesium, nitrogen, potassium and other salt compounds. It will also have varying amounts of household chemicals, oils, makeup greases, nutrients and chemicals that can largely be managed by the types of products used within a household.

Many of the nutrients in gray water are exactly the same as the fertilizers we buy at a local store to fertilize our landscapes. By recycling gray water, you can also reduce or eliminate the need to buy expensive fertilizers.

The use of gray water can immediately reduce onsite potable water use during the irrigation season. This saves the household money on its water bill, reduces the energy required to produce the potable water that would have been used on the landscape, and saves energy required at the treatment plant to process this water to tertiary water standards for downstream use.

In New Mexico and Arizona, installing a gray water system does not require a permit for private residential gray water systems that discharge fewer than 250 gallons per day for use onsite for gardening, composting or landscaping irrigation. There are a few restrictions, with the really key tenets being: It cannot be stored for more than 24 hours; it cannot be used in above-ground spray-irrigation systems; and the water should not contain hazardous chemicals derived from activities such as cleaning car parts, washing greasy or oily rags, or disposing of waste solutions from home photo labs or other home occupational activities.  

In New Mexico, the residential development of Skywater in Cloudcroft requires the installation of gray water systems with any new home. In Tucson, Arizona, the city requires the installation of indoor plumbing for a gray water system at the time of construction. The City of Santa Fe has begun promoting and offering rebates of $150–$300 for the installation of “Laundry to Landscape” gray water systems.  These are the leaders in gray water in the Southwest.  

Additionally, some of the gray water leaders are publishing great reference guides:

Now there is even a model ordinance document for jurisdictions to use. This document was written by The Decentralized Water Policy Council and is modeled after the leaders: Arizona and New Mexico regulations. 

The above guides will help others follow. One of the purposes of the upcoming Next Generation Water Summit (NGWS), to be held in Santa Fe on April 29 –May 1, is to share these best practices with others.  The overall focus of the summit is to assist in the acceleration of the adoption of water reuse solutions in the Southwest. The summit will feature water policy professionals and builders/developers from around the Southwest, sharing what works and what does not work. The summit will feature several gray water presentations and a 2-day gray water class will precede the summit at Santa Fe Community College.  

Living within our water budget is key to a sustainable long-term future in the Southwest. We all depend upon the same primary water sources: the Río Grande and the Colorado Rivers. Reusing our water onsite not only makes sense; it helps us stay within our budget. Water reuse is not just for water utilities; it is a solution for us all.

Doug Pushard is a lifetime American Rainwater Catchment System Association (ARCSA) member, an ARCSA Accredited Professional and ex board member. He is co-author of Rainwater Harvesting Industry Market Size and Trends and First-Ever Long-Term Water Conservation Rebate Study. He is also an EPA WaterSense Partner with certification in Irrigation Auditing, an active member of the City of Santa Fe Water Conservation Committee, and one of the organizers of the Next Generation Water Summit.

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