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Greywater systems give tap water a second life

on December 15, 2010

A piece of paper tacked next to Amaro’s washing machine.

A piece of paper is tacked on the back wall of Javier Amaro’s house: “greywater” is written on one side and “sewer” on the other. Below, a pipe coming out of his washing machine runs along the wall. “Normally this washer pipe goes straight to the sewer,” says Amaro, pointing to the tubing. “They put in this other pipe and the shut-off valve.” Amaro is one of hundreds of people in Oakland who have started reusing “greywater”—or run-off water—in their homes. So now when the shut-off valve is open, all the water from his washing machine flows through the new pipe, outside and directly to his garden where he uses it to water his plants.

California’s laws recently changed to allow certain kinds of greywater reuse systems to be installed in homes without requiring permits, so residents are increasingly conserving water from their showers, bathroom sinks, washing machines and more. The collected run-off is usually the kind that stays fairly clean after one use, like bath water—but still, this water isn’t used for drinking or bathing, but rather for watering plants and occasionally for flushing toilets. “Fifty percent of water we use in our homes is greywater and can be reused,” says Juliet Christian-Smith, a senior research associate for the Pacific Institute, an Oakland-based non-profit that works on environmental, economic and social issues.

Proponents of greywater reuse say there are several reasons why people should conserve water in their homes—conservation reduces overall water usage, especially in a state like California that is prone to droughts. Using greywater also preserves the cleanest water for drinking, while avoiding the waste of water that isn’t very dirty. As water sources shrink and droughts become more common and longer lasting, Christian-Smith believes that greywater reuse could be one component of increasing water-use efficiency in the U.S. “Using potable drinking water for every purpose is not something we are going to be able to do for decades into the future,” says Christian-Smith.

Sources of water in a household. Image by NRDC 2009.

In November, the Pacific Institute released a report that examines the potential benefits and challenges of greywater reuse. Studying different laws, regulations and plumbing codes, the report looks at countries most open to reusing greywater, such as Australia, Japan and Spain. It also gives an overview of the different kinds of systems for greywater reuse that are being tried around the world, including mechanisms that reuse sink water to fill toilet tanks and filtration systems that treat and disinfect stored greywater before it’s sent into the ground. The report also looks at drawbacks such as potential public health concerns and having to change public perception to show that reusing greywater is okay.

The washing machine system Amaro has in his Rockridge home is one of the most common greywater reuse methods and saves 5,000 to 10,000 gallons of water a year, depending on the size of the machine and how often laundry is washed. As water empties out of his washing machine and runs through the pipes to his garden, it gets diverted into five more tubes that carry the water to “terminals.” Each terminal is situated somewhere his yard—next to his lemon tree, giant fern, peach tree, geranium plant or his vegetable garden—and the water drains out through them into the surrounding soil, keeping the plants watered. “Basically we don’t have to do much,” says Amaro. “I just go and check the terminals and make sure they are not clogged.”

One of the “terminals” in Amaro’s garden.

Amaro had his system installed last July after taking a workshop from Greywater Action, an Oakland-based organization that works on sustainable water projects. Using Amaro’s house as a demonstration model to teach people how to build systems in their own homes, instructors showed Amaro and the group how to install new pipes and set up terminals. After three hours of work, the entire system was up and running, Amaro says, and the cost for this whole set-up was $200 worth of materials. The cost would be a bit more if he had paid for labor. Other types of home greywater reuse systems range from using a bucket to collect excess water in your shower to re-working your house’s entire plumbing so that all greywater is diverted for reuse.

One of the founding members of Greywater Action, Laura Allen, was one of the instructors who helped build Amaro’s system; she says that not only does greywater reuse conserve water, it also cuts down on people’s monthly water bills and ultimately the state’s electricity usage, because it reduces the amount of water being sent to the wastewater treatment plant. In California, Allen says that the treatment and movement of water consumes 19 percent of all electricity and 32 percent of all natural gas used in the state.

Historically in California, the approach to water management was a “hard path,” meaning that water was moved from the Sierra Nevada mountains to drier parts of the state via dams, canals and pipelines, explains Christian-Smith. “For this area of California, we are dependent on snow melt for a large portion of our water supply,” she says. “Some of the scariest data is the mapping of snowpack with different climate change scenarios.” If temperatures rise as a result of global warming, California could lose half of its snowpack by 2050 and 80 percent could be gone by 2100, she says. “We are facing a new climate reality, we need to start adapting to be resilient to these climatic changes,” she says.

Laura Allen and the group of students learning how to install a greywater system in Amaro’s garden.

The Pacific Institute is advocating for greywater reuse as one of those adaptations. “Now what we are trying to think about is smarter, innovative ways of providing water to people that is more locally based,” says Christian-Smith. “This is the ‘soft path,’ which is more energy conscious.”

However, reusing greywater does offer some challenges. These systems can be expensive to install—while a washing machine method like Amaro’s is relatively low-cost, switching out your house’s entire plumbing to make it drain to reservoirs within the home instead of the sewer could cost up to $15,000 depending on the type of system. Then there’s maintenance. Not only do plumbers and landscapers need to become trained in a whole new skill set, but homeowners also need to learn how to keep their systems running efficiently.

Most cities also have concerns about residents reusing greywater. Some public health departments say that there is the potential for the spread of disease and contamination of the water table if people don’t install and use the systems correctly, and some in the plumbing industry see greywater reuse as back-tracking on technology advancements and centralized sewage management systems that have worked to flush all non-potable water away. Under California law, having pooled and standing water—where bacteria can breed— is illegal, so this eliminates many of the disease threats says Christian-Smith. She also notes, in the institute’s report, that there have been no documented cases of public health impacts of greywater reuse. But, she says, “We still see a need for longer term studies on impacts on health and the environment. Some research gaps still need to be filled.”

Average indoor residential water usage. Image by Pacific Institute, data from AWWA 1999.

Having a clean and healthy greywater reuse system requires education, she says. “If you’re not just sending your greywater off to a sewer system, you need to know what’s going into it,” says Christian-Smith. People who use greywater systems in their homes cannot use bleach or soaps with boron; also, the soap must be liquid because most powder soaps contain salt. Bleach, boron and salt can be toxic to plants. Also, greywater reuse is not good for lawns because the water needs to be applied to each plant’s root system—lawns tend to be too big for water to reach each blade of grass. “It’s easy to do it wrong,” says Allen from Greywater Action. “It’s the best for trees—the bigger the better—and work your way down and stop when you get to small plants like lawns and pansies.”

But overall, Amaro says that learning how to use his system wasn’t difficult. “As a renter it’s simple and cheap,” he says. “If I was the owner, I would think of incorporating it to the shower and the sink, too, but that involves plumbing.”

For people interested in seeing if a greywater reuse system would work in their home, the Pacific Institute has a Water-Energy-Climate calculator (WECalc) on their website. After asking a series of questions, WECalc estimates people’s water and water-related energy consumption and gives recommendations for best lowering their use along with the cost of their water bill.

Lead image: Javier Amaro stands in his garden that is watered with run-off water from his washing machine.


  1. […] undertake for little money, like prohibiting fuel-powered leaf blowers and easing restrictions on residential greywater systems. “We can have a lot of impact with little money spent,” she said. She also said it was […]

  2. […] Published December 15, 2010 on Oakland North […]

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