woman watering garden from watering can

“Graywater” is a term bandied about by those in sustainability circles and a topic we’ve touched on frequently at Earth911, but many still have questions about exactly what graywater recycling is and if it’s really safe for the environment.

So, what’s the verdict? Is this idea green or gross? Earth911 took an in-depth look at the subject to give you the basics and answer all of your most pressing questions about this unconventional recycling tactic.

This is a sponsored post from The American Cleaning Institute

Graywater 101

If you’re unfamiliar with this type of recycling, the No. 1 question on your mind is likely: What is graywater, anyway?

To put it simply, graywater is water from bathroom sinks, tubs, showers and laundry washing machines. Despite frequent confusion, graywater does not include water from toilets, kitchen sinks and automatic dishwashers (this is called “blackwater”) and has not come into contact with food and human waste, either through kitchen sink food waste disposal or flushing toilets.

Graywater may contain traces of dirt, food, grease, hair and certain household cleaning products. While Graywater may look “dirty,” it is a safe and even beneficial source of irrigation water, according to the advocacy group Greywater Action (The spellings of “greywater” and “graywater” are often used interchangeably in discussions about this topic).

As potable water supplies become more limited throughout the world, there is a growing interest in innovative approaches to water resources sustainability, and household graywater reuse for residential landscape irrigation is a potential solution that’s slowly picking up steam.

Graywater recycling offers scores of benefits; plants can beneficially utilize the constituents found in graywater as valuable nutrients. However, the use of such systems has not yet become widespread due to uncertainties about the safe use of graywater, according to a report released by the Water Environment Research Foundation in partnership with the American Cleaning Institute.

While some states have begun to legalize and regulate the practice of graywater reuse for residential landscape irrigation, little guidance based on scientific data has been provided for the safe operation of graywater irrigation systems and the potential effects on plant health after graywater is applied.

“As more households turn to graywater for their irrigation needs, it is important to understand what compounds are in graywater, what happens to them in the environment, and what potential impacts graywater may have on soil quality, groundwater quality, and plant health,” said Kathleen Stanton, ACI’s Director of Technical & Regulatory Affairs.

The WERF/ACI project began in May 2008 and went on for more than four years. The aim: to provide scientifically-based data on the use of graywater and its impacts on soil quality and plant health. It also tried to address public health concerns stemming from potential exposure to elevated levels of E.coli and product ingredients in soils where graywater has been applied. Read on for the details.

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