Graywater 101: Using Graywater to Green Plants?

woman watering garden from watering can

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Is it really safe?

The main debate surrounding graywater safety is how residues (such as dirt or household cleaning products) may effect soil composition and plant and human health if reintroduced to local ecosystems in the form of landscape irrigation.

As part of their five-year-long project, WERF and ACI conducted experimental studies in three parts (existing household systems, new household systems and greenhouse studies) to come up with evidence-based answers to these vital questions.

According to the study: “The research team found that most landscape plants are healthier under long-term graywater irrigation compared to freshwater irrigation. Among 22 plant species evaluated, the research team only observed three species (avocado, lemon tree and Scotch pine) that were sensitive and showed reduced growth, leaf burning, or reduced fruit production under long-term graywater irrigation.”

The bottom line: Gross or green?

The team noted that further research is required for definitive answers on how graywater irrigation impacts a wider variety of plant species, but no major concerns were identified in the study that would render reuse of graywater following best management practices unsafe for growing garden plants or irrigating landscapes.

When using best practices such as those employed in Arizona, human health impacts were also determined to pose minimal concerns.

So, we’re putting a big “green” stamp on this one, but what do you think? Would you feel comfortable watering your garden plants with graywater? Why or why not? Join the conversation in the comments section and on social media.

Editor’s Note: Earth911 partners with many industries, manufacturers and organizations to support its Recycling Directory, the largest in the nation, which is provided to consumers at no cost. The American Cleaning Institute is one of these partners.

Feature photo by bruce mars from Pexels

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  1. So, I stumbled upon this article because I wanted to water my garden with my kids bath water, but wanted to find out more info before I just started dumping dirty bath water on to our food supply. The BIG question is, what about all the personal care products we use? Which has lead me to switch what we use to homemade organic products. A lot of products people use are harmful if swallowed or say to rinse throughly if it gets in your eyes, do I really want something that is labeled like that in my water that is going to feed my plants? General landscaping, sure. Food supply, unsure. I went to and found that all of my former personal care and cleaning products were not only toxic to my skin, but toxic to the environment. How does the gray water get cleaned? What remains in the gray water after it’s filtered or cleaned? And, if the plants in this study have done better than those on regular tap water, what is in our tap water? What makes plants healthier with grey water? I think it’s a great step in a good use of grey water, especially areas that are drought prone.

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