Create an Oasis with Greywater: Integrated Design for Water Conservation, Reuse, Rainwater Harvesting & Sustainable Landscaping
Revised and Expanded 6th Edition by Art Ludwig
Create an Oasis describes how to choose, build, and use everything from a simple greywater system that can be made in an afternoon for under $50 to how to integrate greywater with efficient fixtures, user habits, plant selection and location, rainwater,and freshwater irrigation optimally for your site.
On this page:
Create an Oasis with Greywater describes how to choose, build, and use 17 types of residential greywater reuse systems in just about any context: urban, rural, or village. It explains how you can put together a simple greywater system in an afternoon for under $50. It also includes information for taking your greywater reuse to the next level: integrating it with water efficiency, rainwater use, and food production. This book includes:
- How to clarify your goals, and how various greywater system options can serve you
- The same greywater site assessment checklist and procedures I use for my design consulting
- Common mistakes and how to avoid them
- Greywater plumbing principles and procedures in detail
- Information on soils and plants, tools and parts
- Several of our own original design innovations to improve greywater systems' longevity, simplify maintenance, and reduce environmental impacts
- Real-life examples of greywater designs for a wide range of contexts
This book offers underlying design principles as well as design specifics. If you run into a situation not specifically covered, you'll likely be able to use these general principles to figure it out yourself.
Most of the world’s aquifers are being pumped faster than replenished, and all reservoirs are slowly diminishing in capacity as they fill with sediment. At the same time, natural surface waters and groundwaters are being degraded by the wastewater continually dumped into them. Greywater reuse enables you personally to do more with the same amount of water and to increase your water security. At the same time, your greywater reuse reduces the problems of supply and pollution for everyone.
Any greywater system will realize some benefits. Obtaining all the potential benefits is trickier than it seems. Many pitfalls await the unwary. In the average installation, this book will pay for itself many times over in savings on construction, maintenance, and errors avoided.
Most of the information otherwise available on greywater comes from vendors. Oasis Design doesn’t sell greywater systems, so you don’t have to worry that we’re steering you toward stuff you don’t need. Rather, we make our living by providing information to help people have a higher quality of life with lower environmental impact.
Wishing you the best of luck with your projects,
First, let’s get your feet wet (so to speak)—what is greywater, what can you do with it, why, how, and some greywater lingo.
What Is Greywater?
Any wastewater generated in the home, except water from toilets, is called greywater. Dish, shower, sink, and laundry greywater comprise 50–80% of residential “wastewater.” Greywater may be reused for other purposes, especially landscape irrigation.
Toilet-flush water is called blackwater. A few systems that can safely recycle toilet water are included in this book.
Contaminated or difficult-to-handle greywater, such as solids-laden kitchen sink water or water used to launder diapers, I call “dark greywater”; most regulators consider these blackwater. However, the level of pathogens in even the darkest greywater is a small fraction of that in blackwater.1
Wastewater without added solids, such as warm-up water from the hot water faucet, reverse-osmosis purifier drain water, or refrigerator compressor drip, is called clearwater.
Reclaimed water is highly treated mixed municipal greywater and blackwater, usually piped to large-volume users such as golf courses via a separate distribution system. It is outside the scope of this book.
What Can You Do with Greywater?
Conventional plumbing systems dispose of greywater via septic tanks or sewers. The many drawbacks of this practice include overloading treatment systems, contaminating natural waters with poorly treated effluent, and high ecological/economic cost.
Instead, you can reuse this water. The most common reuse of greywater is for irrigation—the focus of this book. It can also be cascaded to toilet flushing or laundry. Even a greywater-only dispersal system has less negative impact than septic/sewer dispersal, because the beneficial bacteria and roots in the topsoil are better than anything else at treating water.
Why Use Greywater?
It is said that there is no such thing as “waste,” just misplaced resources. Greywater systems turn “wastewater” and its nutrients into useful resources. Why irrigate with drinking water when most plants thrive on used water containing small bits of compost?
Unlike many ecological stopgap measures, greywater use is part of the fundamental solution to many ecological problems. It will probably remain an essentially unchanged feature of ecological houses in the distant future. The benefits of greywater recycling include:
- Reduced use of freshwater—Greywater can replace freshwater for some uses. This saves money and increases the effective water supply, especially in regions where irrigation is needed. Residential water use, on average, is almost evenly split between indoors and outdoors. Most water used indoors can be reused outdoors for irrigation, achieving the same result with less water diverted from nature.
- Less strain on septic tanks or treatment plants—Greywater, which comprises the majority of the wastewater stream, contains vastly fewer pathogens than blackwater and 90% less nitrogen (a nutrient that is a problematic water pollutant). Reducing a septic system's flow by getting greywater out greatly extends its service life and capacity. For municipal treatment systems, decreased flow means higher treatment effectiveness and lower costs.
- More effective purification—Greywater is purified to a spectacularly high degree in the upper, most biologically active region of the soil. This protects the quality of natural surface and groundwaters. Topsoil is a purification engine many times more powerful than engineered treatment plants, or even in septic systems, which discharge wastewater deeper into the subsoil.3
- Feasibility for sites unsuitable for a septic tank—For sites with slow soil percolation or other problems, a greywater system can partially or completely substitute for a costly, over-engineered septic system. (In extreme cases this can enable otherwise undevelopable lots to be built on—a double-edged sword environmentally.)
- Reduced use of energy and chemicals—Due to the reduced amount of freshwater and wastewater that needs pumping and treatment. If you provide your own water or electricity, you’ll benefit directly from lessening this burden. Also, processing wastewater in the soil under your fruit trees definitely encourages you to dump fewer toxins down the drain.
- Groundwater recharge—Greywater application in excess of plant needs recharges the natural store of water in the ground. Abundant groundwater keeps springs flowing and trees growing in intervals between rains.
- Plant growth—Greywater can support a flourishing landscape where irrigation water might otherwise not be available.
- Reclamation of nutrients—Loss of nutrients through wastewater disposal in rivers or oceans is a subtle but highly significant form of erosion. Reclaiming otherwise wasted nutrients in greywater helps to maintain the land’s fertility.2,3
- Increased awareness of, and sensitivity, to natural cycles—The greywater user, by having a reason to pay more attention to the annual progression of the seasons, the circulation of water between the Earth and the sky, and the needs of plants, benefits intangibly but greatly by participating directly in the wise husbandry of vital global nutrient and water cycles.
- Just because—Greywater is fairly harmless and great fun to experiment with. Moreover, life with alternative waste treatment is less expensive and more interesting...
Does Greywater Matter? (excerpt)
Viewed from any single, narrow perspective, greywater systems don’t look that important. A low-flow showerhead can save water with less effort. A septic system can treat greywater almost as well.
But when you look at the whole picture—how everything connects—the keystone importance of greywater is revealed.
Ecological systems design is about context, and integration between systems. The entirety of integrated, ecological design can be reduced to one sentence: do what's appropriate for the context.
Ecological systems—rainwater harvesting, runoff management, passive solar, composting toilets, edible landscaping—all of these are more context sensitive than their counterparts in conventional practice; that's most of what makes them more ecological.
And greywater systems are more context sensitive than any other man-made ecological system, and more connected to more other systems.
Get the greywater just right, and you’ve got most of the whole package right, and that’s what matters.
Branched Drain (excerpt)
For sites with continuous downhill slope from greywater source to
irrigated areas, Branched Drain systems provide inexpensive, reliable,
automated distribution with almost no maintenance. Branched Drains have
no filter, pump, surge tank, or openings smaller than 1" (2.5 cm).
All variations of this system meet legal requirements in Arizona and other
states that regulate greywater rationally. A friendly inspector can issue a permit for this system under the CPC/UPC. Chapters 9 and 10 explore every aspect of Branched Drain systems in detail.
The Laundry to Landscape (L2L) system is the simplest, least expensive, lowest-effort way to get the most greywater onto the home landscape. It is the greywater system most suited for professional installation by landscapers, yet it is also DIY and renter-friendly. Odds are it makes sense for you…and even if not, like the Branched Drain chapters, this section intersects some important
greywater design principles from a new angle and is worth reading. (The L2L is an Art Ludwig
original design, developed to address the need for a more prime-time-ready laundry greywater
system when California agreed to our request to make laundry-only systems permit-exempt.)
Laundry to landscape (web-updated)
In practice, the health risk of greywater use has proven minimal to nonexistent. It is, after all, the water you just bathed in, or the residue from clothes you wore not long ago. Despite all sorts of grievous misuse (brought on in part by lack of useful regulatory guidance), there has not been a single documented case of greywater-transmitted illness in the US. Nonetheless, greywater may contain infectious organisms. It's poor form to construct pathways for infecting people, and totally unnecessary. Keep this in mind when designing and using a system.
All greywater safety guidelines stem from these two principles:
- Greywater must pass slowly through healthy topsoil for natural purification to occur.
- Design your greywater system so no greywater-to-human contact occurs before purification.
Here are examples of possible health-related greywater problems and their solutions:
- Direct contact or consumption—Solutions: Carefully avoid cross connections (accidental connections between freshwater and greywater plumbing). Label greywater plumbing, including greywater garden hoses. Use gloves when cleaning greywater filters. Wash your hands after contact with greywater.
- Microorganisms on plants—Direct application to foliage can leave untreated microorganisms on surfaces. Solution: Don’t apply greywater to lawns, or to fruits and vegetables that are eaten raw (e.g., strawberries, lettuce, or carrots). Greywatering fruit trees is acceptable if the greywater is applied under mulch.
- Pathogen overload—Greywater systems are safest when reusing water that is fairly clean initially. Solutions: Greywater should not contain water used to launder soiled diapers or generated by anyone with an infectious disease. In both cases, greywater should be diverted to the septic tank or sewer. Also, don't store greywater; use it within 24 hours, before bacteria multiply.
- System overload—If you are having a party and 50 people are going to use a system designed for two, consider diverting greywater to the sewer for the night.
- Breathing of microorganisms—Droplets from sprinklers can evaporate to leave harmful microorganisms suspended in the air, where people may breathe them. Solution: Don’t broadcast greywater with sprinklers.
- Chemical contamination—Biological purification does not usually remove industrial toxins. Toxins will either be absorbed by plants or pollute groundwater. Many household cleaners are unsuitable for introduction into a biological system. Solutions: Divert greywater that contains chemicals so they poison the sewer or septic instead. Better yet, don't buy products that you wouldn't want in your greywater system.
- Contamination of surface water—Greywater needs to percolate through the soil, or else it might flow untreated into creeks or other waterways. Solutions: Discharge greywater underground or into a mulch-filled basin to contain it and slow its movement toward surface waters or groundwater. Don’t apply greywater to saturated soils. Apply greywater intermittently so that it soaks in and the soil can aerate between waterings. In general, greywater that is confined subsurface or within mulch basins at least 50' (15m) from a creek or lake is not a problem.
- Contamination of groundwater or well—It is all but impossible to contaminate groundwater with a greywater system, as the treatment capacity of the topsoil is so enormous. Over 90% of plant roots and beneficial microorganisms are in the top few feet of soil, above most septic leachfields. However, if you have a poorly sealed well, greywater running over the surface could potentially pour into it. Solution: The CPC/UPC greywater codes, which are just crude adaptations of septic tank codes, call for 50' of separation between location of greywater application and a well, same as a septic. Probably half of this is sufficient.
- Common greywater mistakes
- System selection chart-pdf
- GW site assessment checklist-pdf
- Greywater links
- Book index (HTML or PDF)
What This Book Is About
Chapter 1: Greywater Basics
What Is Greywater? • What Can You Do with Greywater? • Why Use Greywater? • When Not to Use Greywater • Elements of a Greywater System
Chapter 2: Goals and Context
Get Clear on Your Goals
Assess Your Context
Greywater Systems Are Very Context Dependent • Site Assessment Example • Does Greywater Matter? • Side Trips and Shortcuts That May Apply to You
Assess Your Site
Assess Your Water Resources • Evaluate Conservation Options • Assess Existing Wastewater Treatment Facilities • Assess Your Greywater Sources • Check the Slopes and Elevations •Units: gpd, gpw, gpy, or gpdc? • Help! Too Many
Numbers! • Check the Soil Perk • How to Measure Perk v Assess Your Treatment/Dispersal Area • Assess Your Irrigation
Need • Assess the Climate and Forces of Nature • Assess the Regulatory and Social Climate • Appraise the People Part of
the System • Cost-Benefit Analysis • A Note on Lawns • Lawn Statistics
Revisit Your Goals
Chapter 3: Design for Your Context
Integrate Greywater with Other Systems
Health Considerations • Six Factors for Good Natural Purification of Water or Wastewater • Coordinate with Others • General Landscape Design Points • General Landscape Design Points
Connect Greywater Sources with Irrigation or Dispersal Area
Lump or Separate the Greywater Flow? • Multiple Greywater Zones • Provide for Maintenance and Troubleshooting
Practice Optimal, Integrated Design
Relate Well with the Natural Water Cycle
Chapter 4: Greywater Collection Plumbing
General Greywater Plumbing Principles
When to Get Professional Help • Squander No Fall • Collection Plumbing and Inspections • Build for Future Flexibility • Divert Greywater Downstream from Traps and Vents • Note on Surge Tank Collection Plumbing • Provide Cleanouts and Inspection Access • Design for Easy Maintenance and Troubleshooting
Collecting Laundry (Pressurized) Greywater
Collecting Gravity-Flow Greywater
Pre-Filter Surge Capacity in Collection Plumbing • Surge Tanks • Surge Capacity in Irrigation Piping• Surge Capacity in the Receiving Landscape • Dosing Siphon
Choosing and Finding Parts
Minimize Plastic Impact • Proper Fittings and Optimal-Size Pipe • Valves
Tools for Collection Plumbing
Radical Plumbing: A Fraction of the Resource Use
Chapter 5: Greywater in the Landscape
How Much Area Do You Need for Treatment/Dispersal? • Coordinate with Freshwater Irrigation, Actualize Water Savings • Irrigation Efficiency • Get Your Freshwater Irrigation Under Control • Choose the Proportion of Irrigation to Meet with Greywater • How Much Area Should You Irrigate? • Effect of Soil Type on Irrigation Design • Effect of Rainwater Harvesting and Runoff Management • What to Do with Greywater When Plants Don’t Need It
Preserving Soil Quality
Garden-Friendly Cleaners • Urine and Salt Balance • The Key Role of Rainwater • Monitoring and Repairing Soil • Toxic Waste Disposal
Plants for Greywater Reuse • Plants for Greywater Treatment/Dispersal
Mulch Basin Design
Mulch • Basins • Infiltration Capacity of Greywater Mulch Basins • Swales • Post Holes and Auger Holes
Chapter 6: System Selection Chart
Chapter 7: Simple, Easy Greywater Systems
C: Collection Plumbing; I: Irrigation Plumbing; R: Receiving Landscape
Landscape Direct (CIR) • Drain to Mulch Basin/Drain Out Back (CIR) • Movable Drain (IR) • Branched Drain (IR) • Laundry Drum (CIR) • Laundry to Landscape (CIR) • Ecological Laundry • Tools for Transition to Outdoors • Getting Even Distribution • Experimental Adaptations for High-Efficiency Washers • Garden Hose through the Bathroom (CIR) • Dishpan Dump/Bucketing (CIR) • Mulch Basins (R) • Greywater Furrow Irrigation (CIR)
Chapter 8: More Complex Greywater Systems
Drum with Effluent Pump (I) • Subsoil Infiltration Chambers (R) • Solar Greywater Greenhouse (R) • Doug and Sara Balcomb’s Solar Greenhouse in Santa Fe, NM • Green Septic: Tank, Flow Splitters, and Infiltrators (CIR) • Blackwater Reuse Health Warning • Constructed Wetlands (IR) • Automated Sand Filtration to Subsurface Emitters (IR) • Advanced Treatment System to Subsurface Drip (CIR)
Chapter 9: Branched Drain Design
Lessons Learned from the Drain Out Back
Branched Drains to the Rescue
Split the Flow • Contain and Cover the Flow
Advantages and Disadvantages of Branched Drain Systems
Limitations of the Branched Drain System
Branched Drain System Design
Ways to Split the Flow • Parts for Splitting the Flow • Branching Geometry Options • Reductions • Cleanouts, Inspection Access, and Rainwater Inlets • Branched Drain Outlet Design • Mulch Basin Surge Capacity • Branched Drain Mental System Check-Out
Chapter 10: Branched Drain Installation
Double-Check Your Design • Check for Buried Utilities • Dipper Installation • Connect Pipes and Fittings on the Surface without Glue • Dig Trenches • Laying Pipe with Plenty of Slope • Laying Pipe with Marginal Slope • Form Mulch Basins, Install Outlet Chambers, and Plant Trees • System Test • Map the System • Cover Up
Branched Drain Maintenance
Branched Drain Troubleshooting
Branched Drain Variations, Improvements, and Unknowns
Chapter 11: Common Greywater Errors
Error: Assuming It’s Simple • Error: Out of Context Design • Error: Overly Complex, Delicate, and/or Expensive System with Negative Net Benefit • Context Specific Design • Error: Mansion with a Greywater System • Error: Pump Zeal • Error: Storage of Greywater • Error: Paranoia about Negligible Health Concerns and/or Cavalier Disregard for Legitimate Public Health Concerns • Error: Treatment Before Irrigation • How Dangerous Is Greywater? • Error: Discharge of Greywater Directly to Natural Waters or Hardscapes • Error: Greywatering Lawns • Error: Irrigating Vegetables • Error: Irrigating Plants That Can’t Take It or Don't Need It • Error: Garden Hose Directly from the Washer • Error: Perforated Pipe or Other System Where You Can’t Tell or Control Where the Water Is Going • Error: Combined Wastewater Designs Used for Greywater • Error: Freshwater Designs and Hardware Used for Greywater • Error: Inexpensive Greywater-to-Drip Irrigation • Error: Low-Volume Automated Greywater Toilet-Flushing Systems • Error: Use of Government Agencies, Engineering Firms, or Salespeople for Greywater Design • Error: Guidance from Work-in-Progress Codes
Chapter 12: Real World Examples
Example #1: Town—City of Santa Barbara (Branched Drain) • Example #2: Suburbia—Southern California (Branched Drain) • Example #3: No Water—Highland Central Mexico (Various) • Example #4: Too Wet—Oregon (Mulch-Covered Bog) • Example #5: Big Family in New House (Automated Subsurface Emitters)
Where to Go for More Information
The Future of Greywater Use
Appendix A: Site Assessment Form
Appendix B: Measuring Elevation and Slope
Appendix C: Cold Climate Adaptations
Appendix D: Greywater in the Non-industrialized World
Greywater Furrow Irrigation
Appendix E: Pumps, Filters, and Disinfection
Appendix F: Related Aspects of Sustainable Water Use
Natural Purification • The Household Water Cascade • Natural Purification by Soil Bacteria and Plant Roots • Rainwater Harvesting • Composting Toilets
Appendix G: Greywater Regulation Revolution
Arizona Greywater Law
Appendix H: Measurements and Conversions
Further Reading and Resources • Suppliers
About the Author
House Features After Water Makeover