Pipe Dreams: The Basics of Graywater Systems

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A graywater system reuses water from sinks, showers, tubs, dishwashers and washing machines to water gardens and landscaping.

Though 70 percent of the earth’s surface is covered with water, only about 1 percent of that is suitable for human use–and we are gulping this precious resource at ever-expanding rates. As world population grows steadily, our water use doubles every 20 years. Water tables are falling and pollution renders more water unusable.

But fear not! It’s easy to make a big difference simply by reusing some of the water that needlessly flows out of our household drains. Graywater, the used water from sinks, showers, tubs, dishwashers and washing machines, represents 50 to 80 percent of home “waste” water. Rather than sending it to treatment plants, you can redirect it to your yard and garden and let nature’s filter do its work.

Every Plan is Custom

For generations, people have washed their dishes in a basin, then dumped the water on the flowerbed–and that’s graywater use at its simplest. If you can access your sink drain, you can remove the P-trap, collect drain water in a bucket and use that water to flush the toilet. With just a bit more effort and some inexpensive tubing, you can create a safe, plant-loving graywater distribution system suited to your garden and lifestyle.

Graywater is most commonly used for landscape irrigation–a great, resource-effective marriage of nutrient-rich water with plant needs. Each system must be designed and operated in response to the particular circumstances, including climate, rainfall, property size, soil types, lifestyle and landscaping. As graywater guru and author of The New Create an Oasis with Greywater Art Ludwig says, “There are no general principles.”

Two Simple Systems

Though it’s fairly simple, designing a good graywater system does require thought and planning. If you’re handy, you can probably do some reading and learn all you need to design your own system, or you may want to hire a professional (see Resources below for books, website and installer references). The system should be as simple as possible. Pumps, filters and nozzles can become clogged by particulate matter, so it’s best to avoid them altogether. Keeping it simple also makes for an affordable system. Here are two of Ludwig’s favorites:

Branched Drain to Mulch Basins: This is the most direct way to water downslope trees and shrubs with graywater. By tapping faucet and appliance pipes into a graywater waste line, then running a valved pipe through the wall to the outdoors, you can convey water directly from sinks, tubs and showers to your yard. Once outside, you can add a piece of piping called a plumbing wye to create a branched drain, which splits graywater flow and directs it to multiple plants. Branched draining avoids ponding and runoff problems that can occur if you drain to one spot. Once the graywater arrives at a plant, it’s best to run it into a mulch basin–a doughnut-shaped hole dug around a plant, with the excavated soil piled around the hole. The hole is filled with mulch, preferably wood chips, which contain and cover the flow, slow runoff, retard evaporation and provide biological treatment.

Laundry to Landscape: Ludwig calls this “the simplest, least expensive, lowest-effort way to get the most graywater out onto the landscape most effectively.” A diverter valve mounted on the wall behind the clothes washer sends wash water through the wall or window to a hose connection, allowing easy distribution to mulch beds at trees and shrubs. Depending on the setup, you may also need a vacuum breaker, automatic bypass for freezing weather and backflow prevention valve. Not only can this system water downhill plantings, but the washing machine’s pump provides extra oomph to irrigate up to two feet above the top of the washing machine and up to 200 feet away.

Keep it Legal

Graywater systems’ legal status is a hot and ever-evolving topic. Only a few years ago, graywater use was either illegal or outside the law in most of the United States. As water scarcity issues come to the fore, many municipalities are legalizing graywater systems. Check with your local health department. For a general roundup of graywater policies around the country, check out oasis design.net/greywater/law/index.htm.

Not Black and White

Using a graywater system:

? reduces fresh-water demand, saving money and resources.
? saves energy and reduces pollution by sending less water to treatment plants or septic systems.
? recharges the groundwater supply and provides nutrients to the soil.

A graywater system might not be appropriate if you have:

? insufficient space
? inaccessible drain pipes
? extremely impermeable or permeable soil (graywater can pond on the surface or reach the water table unprocessed)
? a very wet or very cold climate
? a location where laws don’t permit graywater use

Healthy Handling

It’s not wise to drink graywater or handle it directly, but with some basic precautions, graywater use is safe. No cases of illness transmitted from a graywater system have been documented in the United States. To be on the safe side, follow these safety tips from graywater expert Art Ludwig.

?  Don’t store graywater for more than 24 hours; bacteria could multiply and transform it to unsafe, bacteria-ridden blackwater.

?  Limit the amount of cleaning supplies.

?  Avoid borax, a plant toxin.

?  Avoid chlorine bleach and non-chlorine bleach with sodium perborate (liquid hydrogen peroxide is nontoxic).

?  Use cleaners with little or no sodium; liquids are better than powders.

?  Avoid cleaners containing whiteners, softeners or enzymes.

?  Don’t distribute graywater via perforated pipe or small nozzles, which are likely to clog.

?  Label graywater components and wear gloves when handling them.

?  Don’t apply graywater via a sprinkler, aerially to lawns or directly to foliage.

?  Don’t apply graywater to storm-saturated soils.

?  Don’t irrigate with graywater near a well.

?  Don’t water vegetables with graywater (use it on ornamentals or on fruit trees via mulch beds).

?  Don’t discharge graywater directly into bodies of water or onto hardscaping.


Oasis Design

Greywater Action

Water Conservation Alliance of Southern Arizona

World Health Organization’s guidelines for safe use of wastewater

How to Implement a Graywater System for Your Garden (video)

Rainwater Harvesting expert Brad Lancaster on Greywater


Further Reading

Create an Oasis with Greywater: Choosing, Building, and Using Greywater Systems by Art Ludwig

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