Southwest Environment

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Department of Soil, Water and Environmental Science
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Tucson encouraging use of “gray water” for irrigation

washing machine gray water system
Photo by Daneb Josue Sanchez
This gray-water system of Brad Lancaster allows water draining from a washing machine to irrigate either a fig tree or an orange tree

By Jack Akinlosotu, May 10, 2010

Steve Apter, a resident of Tucson for the last 27 years, lives in a cozy house nestled in a tranquil Foothills neighborhood. The home blends in well with others nearby that are fixed with the stucco exterior so familiar in the Southwest.  Apter’s house does not appear to have any special features – except that it is equipped with a gray-water system.

He walked over to his washing machine and pulled it back from the wall. “The piping on back of the machine leads to a drip line that I use for my plants,” he said. The pipe drains into his garden, where he grows strawberries and carrots, and waters a Hoptree that he has in his back yard.

Reusing water in homes from sinks, bathtubs, and showers – known as gray water – for irrigation can help conserve that resource. That’s something the state of Arizona recognized in 2007, when it began to implement tax breaks for people who construct gray-water systems.

Apter received a $1,000 tax break in 2008 for having the system installed in his home. This goes back to the Gray Water Conservation Tax Credit law passed in 2005 in Arizona, which states that an Arizona resident can receive 25 percent of the cost, not to exceed $1,000, toward installing a gray-water system.

On June 1, the City of Tucson began requiring that developers of new homes provide plumbing that homeowners can easily convert to gray-water systems.

On the surface, using gray water seems like a great idea that could appeal to people throughout the United States.  But of course, there are legalities that come along with implementing a gray-water system in homes.

“I really enjoyed getting that tax break in 2008, but there are a few rules that I had to follow in order to stay within the limits of the law with my gray-water system. You have to make sure that you are not using ‘black water’ on your vegetables in the garden,” said Apter. “You don’t want gray water to be ‘sick water’.”

“Black water” is water that has a high content of chemical or food particles that are not suitable for human consumption. Black water typically refers to water from toilets and kitchen sinks that can make people sick if consumed.

The complexities of the systems that people choose to implement can vary greatly. Some people choose simply to collect and distribute water from a leaking sink or filled bathtub. Others may choose to go with a far more complex system, like Apter’s, that involves different piping and requires plumbing skills to install.  

Within homes, there is a possibility of a person having a dual gray-water system which will have piping that can switch between an irrigation line or the sewer system.

Not all plants respond well to gray water, however.

“Acid-loving plants tend to have a hard time with gray water, and certain plants which are native to dry areas have a hard time handling any irrigation in the dry season. Also, some cultivated plants have problems with soggy conditions, “said Charles Graf, the author of gray water guidelines in Tucson

Still, many plants do fine with this recycled water, including most trees.

“As long as I am doing my part to help conserve, I am happy,” said Apter. “Maybe when more people learn about gray-water systems, they will be happy to conserve too.”


Tucson Water information on using Gray Water

Arizona Department of Environmental Quality brochure

Water Conservation Alliance of Southern Arizona (CASA)

Water Harvesting Guidelines in Tucson

Jack Akinlosotu is a Geography student at the University of Arizona. After he graduates in 2011, he plans to go to law school and become an environmental lawyer.

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