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Graywater Reuse

Now that codes are finally getting friendlier, it’s time to start incorporating graywater recycling into landscape plans.

 Untapped Resource

GRAYWATER IS USED household water that has not come into contact with toilet wastewater. It represents two-thirds of a typical household’s indoor water budget. Reusing graywater to irrigate landscaping keeps it onsite and conserves potable water, easing the burden on both water treatment and wastewater treatment plants. Unfortunately, state regulations have made legal use of graywater difficult, if not impossible—although that is changing.

“The regulatory climate has been improving in the last few years,” says Laura Allen, founder of Greywater Action, a California-based non-profit that provides education and other resources for creating water-wise homes. “A lot more states have codes, and California’s updated code is friendlier.”

California used to treat graywater like septic effluent, and the required treatment was prohibitively complicated and expensive. Now, simple systems don’t even require a permit. Arizona and New Mexico boast the most progressive graywater codes, says Allen, with a tiered permitting structure that only requires permits for larger systems. (In Arizona, this means systems that produce more than 400 gallons of graywater per day; in New Mexico, systems that produce over 250 gpd.)

Options and Challenges

Graywater used for irrigation does not have to be treated so long as it isn’t stored, but filtering is essential. (A common misconception, according to Allen, is that filtering cleans graywater. Filtering actually removes larger particles that could clog irrigation equipment.) As long as toxic chemicals or harmful soaps haven’t been used in the home, many plants thrive on graywater, which usually contains some organic nutrients. Allen cites a study in central California that tested graywater on over 1,000 plants, including trees, shrubs and vegetables.

“There was a huge range of plants, all growing happily with graywater,” she says. (Note: although California allows it, some states prohibit graywater reuse on plants grown for human consumption.)

In regions that experience summer drought and lots of winter precipitation, there is the question of what to do with the graywater in winter. Some codes require graywater to be directed into the sewer during such times.

Cold climates present other challenges. The ground may be frozen several months out of the year, making graywater reuse on landscaping impractical. One solution is to use the graywater to irrigate plants in a greenhouse, although this represents a substantial investment (see “An Alternative Septic Solution” below).

Another option is to use graywater for toilet flushing. This can be as simple as capturing graywater in a bucket and pouring it into the bowl. There are manufactured systems that treat and store graywater, then pump it to the toilet when needed, but these tend to be expensive and require energy. In general, using graywater for landscaping irrigation is a better option.

graywater greenhouse

The Warrens’ graywater greenhouse serves as an alternative to a conventional septic system. It treats used water from all fixtures, excepting toilets.

Holding tank

Graywater is filtered before it enters the 165-gallon graywater control tank.

An Alternative Septic Solution
When Carl and Sara Warren decided to convert an old barn on their Berlin, Massachusetts, property into living space, they were faced with the limits of their existing septic system. So they proposed an innovative alternative to the local Board of Health: a composting toilet and “graywater greenhouse.”

The graywater system consists of a 165-gallon graywater control tank and five gravity-fed, mulch-covered “dosing lines,” which irrigate 185 square feet of planting beds. The beds receive an average of 46 gallons of graywater per day. All graywater passes through an effluent filter before entering the control tank; in addition, graywater from the washing machine, shower, kitchen sink and dishwasher is filtered as it leaves each source.

The Massachusetts Department of Environmental Quality required all graywater to be treated by plants—i.e., taken up and evapotranspired—without any possibility of leaching into the soil below the greenhouse, so the Warrens installed a thick rubber membrane and drain-back system, which operates off a sump pump. Hydronic tubing keeps the beds warm, even through bitter Northeastern winters. Carl Warren says the biggest drawback to the system is the cost of heat, and he intends to retrofit the greenhouse with a nighttime insulating system.

The couple chose plants that didn’t mind “wet feet” and that would take up the most graywater. Ornamental banana trees, philodendron, geraniums and other semi-tropical species thrive. The greenhouse has successfully treated graywater for over seven years.

“The biggest maintenance issue is that the plants are so healthy they need to be cut back frequently,” says Carl Warren.

More info: www.warrendesign.com

Gateway to Graywater: The Laundry to Landscape System

graywater containment

Graywater flows through tubing into a mulch shield, which keeps the outlet from clogging with debris. After testing, a lid is attached and the tubing buried.

The average front-loader washing machine uses 40 to 50 gallons per load. Redirecting used water to trees and other landscaping is a simple way to start experimenting with graywater reuse. In many states, such systems don’t require permits. A laundry-to-landscape (L2L) system uses the washing machine’s pump to move graywater through plumbing and into irrigation tubing—up to 50 feet for flat yards, more for downward-sloping sites.

Installing the system requires an afternoon and some basic plumbing skills. The steps are simple. First, create an exit hole for the plumbing that will carry graywater from the appliance to the irrigated areas. Next, install a three-way valve (so you can divert graywater back to the sewer, when necessary) and an air-admittance valve at the system’s highest point. Create mulch basins for trees and shrubs that will receive graywater; this way it won’t run off into other areas of the site. Install irrigation lines by connecting 1-inch poly irrigation tubing to the PVC plumbing, and use ½-inch feeder lines to carry graywater to the mulch basins.

Determining how many areas the system can irrigate involves a number of variables, from the amount of graywater produced weekly to the water requirements of the plants for a given climate. For detailed instructions on designing and installing a system for your clients (or yourself), we recommend Laura Allen’s excellent new book, The Water-Wise Home .

NEX Heater

The NEXheater from Nexus eWater uses a heat pump to extract heat from graywater and heat potable water coming into the tank. The unit can be used with the eWater Collector alone or in combination with the company’s other products.

Mainstreaming Graywater

Graywater makes up two-thirds of all indoor water use. For a family of four living in a WaterSense-certified home, that equals about 40,000 gallons of water that could be recycled annually, says Josh Fuller, manager of sales and marketing for Nexus eWater, an Australian company that specializes in graywater solutions. The company is launching its complete line of graywater recycling products next month. These include a graywater collector, a water heater that extracts waste heat from graywater, the NEXtreater, which treats graywater to “near-potable” standards, and a treated graywater reservoir. These solutions have been demonstrated in KB Home’s Double ZeroHouse projects; now, the company plans to push the concept of the “Recycle-Ready Home”: one that is dual-plumbed and with tanks installed for graywater recycling and storage.

“The concept is similar to the solar-ready home,” says Fuller. “And it can be done for a couple thousand dollars.” Fuller adds that the Nexus eWater system does not break any codes, even in states with no graywater permitting structures in place. When combined with drought-tolerant landscaping, a graywater can meet all irrigation needs of a small- to medium-sized yard; for really small yards, there might even be enough graywater for toilet flushing, as well.

“In a state like California, with strict watering schedules, this allows you to drought-proof your landscaping,” says Bob Hitchner, chief sales and marketing officer for Nexus eWater. He says the company is also working on a solution that integrates rainwater collection with graywater reuse. Treated graywater and rainwater that has been filtered and disinfected with UV treatment would be stored in the same tank and used to irrigate landscaping.


 Image credit: Nexus eWater