In this residential graywater system, water is diverted from points of household use. The lines converge at a filtered and vented surge tank, and there the water can be delivered via an underground irrigation system. Depending on the size and nature of the landscape area, a pump might be needed to assist in irrigation.
Photo Courtesy Home Energy
Steadily increasing human demand for water has caused once-sufficient reservoir and stream supplies to dwindle. Rations are required. Shortages are daily news. Last summer, the usually humid southeastern seaboard experienced an all-time record-setting drought. And H20 became a restaurant beverage with a price tag.
Watching that liquid silver vanish down the drain seems tragic—especially during a drought. Away it swirls into the sewer, barely touching the dinner dishes along the way. Driven by strict watering bans, many households have gotten creative and begun to reuse water from dishwashing, bathing, laundry, and light cleaning—called “graywater”—to nourish landscaping.
Although technically against building codes in most places, the use of graywater has recently become accepted and even encouraged as a residential water conservation measure. The methods for reuse run the gamut in cost, complexity, and water savings, from inexpensive buckets used to toss dishwater on flowers to pricey, whole-house recovery plumbing, tanks, filters, and irrigation systems. Graywater recycling at some level is available—and practical—for almost every household.
There’s no black-and-white definition for graywater, as the name implies. Although it’s possible to flush toilets with it or to reuse laundry rinse water for washing the next load, the most common, practical, and safe graywater application is on residential landscaping. (Note: The term “graywater” also refers to reclaimed runoff, most commonly used by municipalities to water highway medians and roadsides.) To be nature-friendly, garden-directed water should be free of significant solids, harmful bacteria, toxins, and mineral content. Approximately 50 percent of household wastewater may qualify. The other 50 percent includes water from the toilet, considered “blackwater,” and water from softeners, septic systems, and pools. Dishwater from non-vegan homes or water used to wash diapers, heavily soiled or infected clothing, or bedding may also be considered blackwater, containing risky amounts of solids and disease-causing bacteria.
To consider your home’s graywater for reuse, look carefully at what goes down the drain. Does your family use soaps, shampoo, cleansers, and disinfectants that are biodegradable or biocompatible? Green-savvy shopping is essential to maximize graywater collection and minimize stress on vegetation, so read those labels.
What else goes down the drain? The fewer oils and animal products, the better. Chlorine, although extremely toxic to plant life, appears to break down quickly, and small amounts will dissipate in the soil. And remember, every family member or housemate must know the right ingredients—and the wrong ones—for optimal graywater concoction. A list inside the medicine cabinet or on the refrigerator can be a reminder not to rinse questionables in the sink or wash Fluffy’s litter box in the tub.
On the receiving end of the flow is your yard: trees, shrubs, flowers, and ornamentals. Vegetables and fruits intended for raw consumption are not candidates for this type of irrigation. To minimize the risk of getting traces of bacteria, soaps, or toxins on the food you eat, steer clear of pouring graywater on kitchen gardens altogether. Spraying graywater over your grass might not be optimal, either; the risk of bacteria spreading from ground to bare feet, knees, and hands is still unknown, although there are no documented cases of infection or contamination from such.
Choosing a graywater system
Sometimes simpler really is better. Grandmother threw her dishpan water out the back door on the zinnias, and you can too. Bath water—the average soak in the suds uses twenty-four gallons—is relatively easy to harvest if you have a strong back and a bucket contoured to the tub. And don’t forget to collect the water that runs out the tap until warm or the cooking-pot fluids from noodles and vegetables. Even if you drink eight glasses of water a day, much more than that might be re-claimed from the tap; the per capita faucet-water use rate is almost eleven gallons a day. These ultra-simple graywater collection methods under the sink (and under the table) may be your only option in areas where plumbing codes forbid anything else.
If you have sufficient slope, it may be easy to rig a hose siphon from the shower drain, tub, or washing machine directly to the garden. But these systems can cause backwash and backlash. With little added expense and elbow grease, a few upgrades can go a long way toward keeping graywater safe and will conserve even more water.
If sink, tub, and washer drainpipes are accessible through a crawl space, basement, or outside wall, you can divert them into mulch basins or leach fields in your yard.
Although not absolutely necessary when slope and flow are constant and sufficient, graywater collection drums are another good option. Usually placed just outside the house, the drum access pipe or hose has a filter, which eliminates particles that can clog irrigation lines. Graywater should be held for less than twenty-four hours; longer periods cause harmful organic growth, a bad stench, and murky flow.
Choose moveable, above-ground irrigation lines made of flexible tubing or hose. Permanent irrigation lines are harder to flush out, impossible to move when leach fields are saturated or landscaping changes, and are less adaptable to accommodate fluctuating flow volumes and slope. In addition, permanent lines run the risk of freezing; hoses or above-ground systems can be disconnected in winter.
Many more elaborate systems have been designed and can be purchased or built, but the long-term assessments are still out. New construction that includes a home graywater system plumbed alongside sewer and potable water lines may offer the biggest bang for the buck, but without the written approval of local governments, they are seldom built.
The ultimate guidebook for do-it-yourselfers is Art Ludwig’s Create an Oasis with Greywater: Your Complete Guide to Choosing, Building, and Using Greywater Systems (Oasis Design, 1994; updated in 2002). Clear illustrations and descriptions allow you to pick and choose from numerous setups that will adapt to your own home. If local code allows for graywater use—or looks the other way—a plumbing contractor may be helpful, and Ludwig offers a builder’s guide as well.
The future looks gray
The benefits of using graywater are many, beyond simple water conservation. Landscaping makes up as much as 10 percent of home value in some places, and water restrictions on top of drought conditions can kill even the largest trees—and your long-term financial and aesthetic investments. Even smartly xeriscaped plots suffer during drought. Graywater harvesting is an ethical way to rescue your personal oasis.
Yet using graywater does more than revive your yard. Lower sewer flows may increase the longevity of home systems and local infrastructure. Wastewater treatment facilities use another valuable resource—energy—but graywater is immediately “treated” and diverted into the environment. Homes that capture graywater experience increased water conservation awareness and less waste. These households choose biocompatible products over their less desirable counterparts, so the world’s backyard benefits too.
5 tips for graywatering
1. Don’t allow graywater to pool in the garden or lawn, and contain the flow within your own property.
2. If using filters or hoses, check and clean them frequently to avoid backups into laundry rooms or drains.
3. Keep pets and children away from freshly graywatered areas. Thirst or curiosity can put them at risk.
4. Buy buckets to fit the contours of sinks and tubs for easy manual graywater collection.
5. Wash hands thoroughly after any graywater contact.