Gray and Green: Maximizing Use of Graywater

Reusing the water you used to wash and bathe just makes good sense.

| July/August 2003

  • On the receiving end of the flow is your yard: trees, shrubs, flowers, and ornamentals.
  • 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
  • On the receiving end of the flow is your yard: trees, shrubs, flowers, and ornamentals.

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.

Defining gray

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.

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