The New

Create an Oasis with Greywater

Choosing, Building and Using Greywater Systems — Includes Branched Drains

Revised and Expanded 5th Edition    by  

Create an Oasis describes how to quickly and easily choose, build, and use a simple greywater system. Some can be completed in an afternoon for under $30.

It also provides complete instructions for more complex installations, how to deal with freezing, flooding, drought, failing septics, low perk soil, non-industrialized world conditions, coordinating a team of professionals to get optimum results on high-end projects, and “radical plumbing” that uses 90% less resources.

On this page:

“Greywater for dummies and greywater encyclopedia in one  information goldmine.”
—Dan Chiras, author,  The New Ecological Home; The Solar House


$20.95 New Create an Oasis only

New Greywater Book and Video Set: Create an Oasis, Builder's Greywater Guide, Principles of Ecological Design, Laundry to Landscape instructional DVD $49.80 ($13 savings)

Create an Oasis shows you how to:

Other topics include: Why to use or not use grey water, health guidelines, grey water sources, irrigation requirements, twenty system examples and selection chart, biocompatible cleaners, grey water plumbing principles and components, maintenance and troubleshooting, freezing, rain, preserving soil quality , storing rainwater, compendium of common grey water errors and preferred practices, suppliers, and references.

This 5th edition of the world’s best-selling greywater book includes 50 pages of new text, photos, and figures, as well as the entire text of our Branched Drain Greywater Systems book. Do-it-yourself Branched Drains provide reliable, economical, sanitary, low maintenance distribution of household greywater to downhill plants without filtration, pumping, a surge tank, or electronic controls.

This book is of interest to homeowners, do-it-yourselfers, back-to-the-landers, conservationists, gardeners, developers, builders, plumbers, regulators, policy makers, development workers, and researchers.

If your project is going to involve permitting, inspection, codes, or building a system for someone else, writing or applying codes, or greywater research, you will also want our Builder's Grey Water Guide (book). These two are available as a set—seeBooks & articles.


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What This Book Is About

gray water in water cycle
Humans enjoying their role as responsible stewards of the water cycle.

Create an Oasis with Greywater describes how to choose, build, and use 20 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 $30. It also includes information for taking your greywater reuse to the next performance level:

This book offers underlying design principles as well as design specifics. If you run into a situation not specifically covered, there’s a good chance you’ll 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, but 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,


Art Ludwig Parker Abercrombie Michelle Howard

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Chapter 1: Greywater Basics

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.2

Greywater reuse follows the same principles that make wild rivers clean…even though they drain many square miles of dirt, worms, and feces. Beneficial bacteria break down nasties into water-soluble plant food, and the plants eat it, leaving pure water. The author is shown here deeply absorbed in his tireless study of this process.

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 disposal system has less negative impact than septic/sewer disposal.

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:


Does Greywater Matter?

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 entirity 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 manmade 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.


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Excerpt ~ Drain out back

Cutaway view of a double ell, a flow-splitting fitting that is largely self-cleaning with no filtration. This one is part of the first known Branched Drain network. I tested it for half a year: valiantly tried to clog it with pure kitchen sink water—took the sink strainer out and pushed bowls of soggy granola and pot scrapings down the pipe. The
p-trap clogged every other day, but the Branched Drain network never did.

Excerpt ~ Branched Drains to the Rescue

A Branched Drain system solves most of the drawbacks above while retaining most of the advantages. Like the Drain Out Back, it has no pump, filter, surge tank, electronic controls, or any opening smaller than 1", and has maintenance intervals of a year or more.
Unlike the Drain Out Back, it can automatically disperse greywater to several trees with satisfactory efficiency, it is much more sanitary, and it is possible that you could get a permit for it. The difference is that it splits the greywater in a branching network of pipes, then contains and covers the greywater in the landscape by means of mulch-filled basins.


Excerpt ~ Laundry to Landscape

Laundry to Landscape (web-updated)

Laundry to Landscape (PDF 1mb)as it appears in the 2009 printing


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“The Oasis greywater book is a powerful tool for the professional and homeowner alike. As water becomes the commodity this century that oil was in the past, this book will be required reading for those who want to control their own destinies and responsibly steward an increasingly dwindling resource: clean water.”
—Jonathan Todd, President, John Todd Ecological Design

Excerpt ~ Health Considerations

In practice, the health risk of greywater use has proven minimal. 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 United States. 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:

  1. Greywater must pass slowly through healthy topsoil for natural purification to occur.
  2. 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:


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More exerpts

Common grey water mistakes

System selection chart (PDF)

Greywater site assessment/ system checklist (PDF)

Greywater links

Book index— HTML or PDF




Table of Contents

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 • 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 • Check the Soil Perk • How to Measure Perk • Assess Your Treatment/Disposal 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
Revisit Your Goals

Chapter 3: Design a Greywater System for Your Context

Integrate Greywater with Other Systems
Health Considerations • Coordinate with Others • General Landscape Design Points
Connect Greywater Sources with Irrigation or Treatment Area
Lump or Split the Greywater Flow? • Multiple Greywater Zones
Provide for Maintenance and Troubleshooting

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 • Provide Cleanouts and Inspection Access • Design for Easy Maintenance and Troubleshooting
Collecting Pressurized Greywater
Collecting Gravity-Flow Greywater
Surge Capacity
Pre-Filter Surge Capacity in Collection Plumbing • Surge Tanks • Surge Capacity in Distribution Plumbing • 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/Disposal? • Coordinate with Freshwater Irrigation, Actualize Water Savings • Irrigation Efficiency • 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 You Don’t Need It
Preserving Soil Quality
Garden-Friendly Cleaners • Urine and Salt • The Key Role of Rainwater • Monitoring and Repairing Soil • Toxic Waste Disposal
Plants for Greywater Reuse • Plants for Greywater Treatment/Disposal
Mulch Basin Design
Mulch • Basins • Swales • Post Holes and Auger Holes

Chapter 6: System Selection Chart

Chapter 7: Simple, Easy Greywater Systems

Landscape Direct (CDR) • Drain to Mulch Basin/Drain Out Back (CDR) • Movable Drain (DR) • Branched Drain (DR) • Laundry Drum (CDR) • Drumless Laundry (CDR) • Garden Hose through the Bathroom (CDR) • Dishpan Dump/Bucketing (CDR) • Mulch Basins (R) • Greywater Furrow Irrigation (CDR)

Chapter 8: More Complex Greywater Systems

Drum with Effluent Pump (D) • Mini-Leachfields (R) • Subsoil Infiltration Galleys (R) • Solar Greywater Greenhouse (R) • Doug and Sara Balcomb’s Solar Greenhouse in Santa Fe, NM • Green Septic: Tank, Flow Splitters, and Infiltrators (CDR) • Blackwater Reuse Health Warning • Constructed Wetlands (DR) • Automated Sand Filtration to Subsurface Emitters (DR) • Septic Tank to Subsurface Drip (CDR)

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 Check-Out • 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 • Context Specific Design • Error: Mansion with a Greywater System • Error: Pump Zeal • Error: Storage of Greywater • Error: Cavalier Disregard for Legitimate Public Health Concerns and/or Excessive Paranoia about Negligible Health Concerns • Error: Treatment Before Irrigation • Error: Greywater Staying on the Surface • Error: Surface Greywatering of Lawns • Error: Irrigating Vegetables • Error: Irrigating Plants That Can’t Take It • Error: Garden Hose Directly from the Washer • Error: Perforated Pipe or Other Distribution 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: Greywater to Inexpensive Drip Irrigation • Error: Low-Volume Reuse Systems for Toilet Flushing • Error: Use of Government Agencies, Trade Organizations, Engineering Firms, or Salespeople for Design of Greywater Systems • Error: California Greywater Law Used as Model

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 • Example #6: No-Money Ecotourism—Michoacán (Greywater Furrow Irrigation)

Appendix E: Pumps, Filters, and Disinfection

Appendix F: Related Aspects of Sustainable Water Use

The Household Water Cascade • Rainwater Harvesting • Composting Toilets

Appendix G: Greywater Regulation Revolution

Arizona Greywater Law

Appendix H: Measurements and Conversions


Further Reading and Resources • Suppliers


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