Greywater, Green Landscape

How to Install Simple Water-Saving Irrigation Systems in Your Yard


By Laura Allen

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Keep your lawn and garden lush without wasting resources by capturing and recycling the greywater that drains from your sink, shower, and washing machine. This accessible and detailed guide walks you through each step of planning for and installing a variety of greywater systems, including laundry-to-landscape and branched drain gravity-fed systems. After identifying greywater sources in your home and estimating flow rate, you’ll learn to pinpoint where to redirect the wastewater for the greatest benefit. No matter which system you decide to build, you'll have the information to construct it yourself or move forward with confidence to hire a professional. 


To the greywater installers, educators, and users, and especially to Greywater Action



Part 1: Planning Your Home Greywater System

Chapter 1: Greywater Systems 101

What Is Greywater?

Types of Greywater Systems

Health and Safety Considerations

Greywater in Freezing Climates

Chapter 2: Greywater Sources and Plumbing

Identify Your Greywater Sources

Your Home's Drain, Waste, and Vent System

Undesirable Greywater Sources

Summary of Greywater Sources

Chapter 3: Estimate Your Greywater Flows

Code Estimates vs. Personal Calculations

Calculating Weekly Greywater Flows

Finding the Flow Rates of Different Fixtures

Chapter 4: Soils and Mulch Basins

Soil Structure and Type

Identify Your Soil Type with a Soil Ribbon Test

Determine How Water Flows through your Soil with an Infiltration Test

Mulch Basins

Protect Groundwater and Drinking Water Wells

Chapter 5: Plants and Irrigation

Choosing Plants for Greywater Irrigation

How Much Water Do My Plants Want?

Plant-Friendly Soaps

Chapter 6: Choosing a Greywater System

System Design Considerations

When Greywater Is Not a Great Idea

Using Greywater Indoors: Toilet Flushing

Choosing a Greywater Irrigation System

Greywater Systems at a Glance

When to Turn Off the System

Chapter 7: Codes and Regulations

A Brief History of Greywater Plumbing Codes

Greywater Codes: Performance and Prescriptive

National Codes and Standards

Part 2: Building Your Home Greywater System

Chapter 8: Install a Laundry-to-Landscape (L2L) System

Design Considerations

Installing an L2L Irrigation System

Irrigation Options

Chapter 9: Install a Branched Drain Gravity-Flow System

Design Considerations

Installing a Branched Drain System

How to Wire an Actuator

Chapter 10: Pumped and Manufactured Greywater Systems

Design Considerations

Building a Pumped System

Manufactured Greywater Systems

Chapter 11: Other Types of Greywater Systems

Outdoor Fixtures

Whole-House Greywater Systems

Subsoil Infiltration Systems

Greywater for Greenhouses

Constructed Wetlands

Sand Filter to Drip Irrigation

Reusing Septic Tank Effluent for Irrigation


Plumbing Basics for Greywater Installation

Parts Primer

Basic Installation Techniques




Grow Your Own Green Library with More Books from Storey


Share Your Experience!


In August 2012 I sat in a radio studio talking about greywater with my former plumbing teacher — and, at the time, Oakland's senior inspector — Jeff Hutcher, on American Public Media's The Story. When I met Jeff in 1999, I never would have imagined this moment. I was a student in his residential plumbing class, seeking to learn hands-on skills to build sustainable water systems. At the time, he was horrified to hear about my "Frankenstein" greywater setups and refused to answer questions about my then-illegal plumbing systems in class (he was, after all, a city inspector). Now he and I work together to streamline permits and facilitate legal reuse of greywater.

Greywater Action Los Angeles in 2016. Left to right: Ty Teissere, Laura Allen, Cris Sarabia, Laura Maher, Sergio Scabuzzo

For the past 17 years, I've designed and built simple residential water reuse systems: greywater systems, rainwater catchment, and composting toilets. Once my friend and housemate Cleo Woelfle-Erskine and I cut into our home's plumbing to channel the shower water outside. I couldn't imagine ever again letting this good irrigation water escape to the sewer. We taught our friends and wrote about the how and the why of it. Our group, the "Greywater Guerrillas," grew out of these projects. Later, we worked on an anthology, Dam Nation: Dispatches from the Water Underground, which placed greywater reuse, rainwater catchment, and composting toilets in the larger political context of water issues around the globe.

Some genuine plumbers joined our group: Christina Bertea, the first woman admitted into Local 159, Plumbers and Steamfitters Union, and Andrea Lara, then an apprentice. With their involvement, we honed our skills and revamped our designs. Andrea, Christina, and I taught dozens of hands-on workshops all over the Bay Area and southern California. As our state entered a multi-year drought, we couldn't keep up with the demand. Every workshop filled up, along with the wait list. I gave talks at green-living festivals, universities, churches, and even high schools.

Since all our work was illegal, according to state plumbing code at the time, we became involved in changing the code. In 2009 the State of California overhauled its greywater code, making many greywater systems legal. That same year we renamed our group "Greywater Action: For a Sustainable Water Culture," to represent our goals and strategies to a diverse audience.

We continue to teach hands-on workshops, as well as trainings for professionals who want to offer these services to their clients. In our one-week class we teach people theory and hands-on skills, culminating with the participants installing a real system on the last day of class. Over a hundred people from across the U.S. and Canada have graduated and now champion greywater in their communities. Their systems, businesses, and workshops are the ripple effects of their training.

Our work expanded from the Bay Area to Southern California, where I lived for the past few years, with new members, bilingual (English/Spanish) trainers and materials, and partnerships with forward-thinking water agencies.

Now I live in Oregon and am adapting greywater into a new climate region.

I hope this book helps you tap into your own greywater resources and grow a beautiful, productive landscape.

Brian Munson on left, Christina Bertea on right

Part 1

Planning Your Home Greywater System

If you're like most people, you wash clothes, take showers, and run water down the sink. Why let this good irrigation water go to waste? Surely you've heard the expression, "Don't throw the baby out with the bathwater." Now, let's stop throwing out the bathwater!

This part of the book — chapters 1 through 7 — takes you through the initial design and planning steps for building a greywater system. A successful system is tuned to match your water usage, your home's plumbing, and your landscape. Here, you'll learn how to estimate how much greywater your home produces, which greywater sources (called fixtures) you can tap into, and how to test your soil and size the mulch basins (to receive the greywater in your landscape). You will also learn about the types of plants that grow well with greywater and which soaps and products are safe to use. In addition, we'll look at some basic health and safety considerations and regulations for greywater. After you've done the preparation work, Part 2 — chapters 8 through 11 — will take you step-by-step through the installation of various systems.

Don't forget to start with efficiency. Before planning your greywater system, make sure your home is water-efficient. Fixing leaks and upgrading fixtures can reduce indoor water consumption by around 35 percent. See the Resources section for more information.

Chapter 1

Greywater Systems 101

The first step to design and install a greywater system is to understand your options.

These include the different types of systems, their general costs, their strengths and limitations, their benefits, and their health and safety considerations. This chapter provides the foundation you'll need for the details and calculations in the upcoming chapters.

Home using greywater for irrigation with simple laundry-to-landscape and gravity-fed systems

In this chapter:
  • Water Saving Potential and Costs
  • Pros and Cons of Using Greywater
  • Types of Greywater Systems
  • Health and Safety Considerations
  • Greywater in Freezing Climates

What Is Greywater?

Greywater is gently used water from sinks, showers, baths, and washing machines; it is not wastewater from toilets or laundry loads containing poopy diapers. Plants don't need clean drinking water like we do! Using greywater for irrigation conserves water and reduces the energy, chemicals, and costs involved in treating water to potable quality.

Reusing water that we already have is a simple and commonsense idea. Just use "plant friendly" soaps (those low in salts, and free of boron and bleach), and you have a good source of irrigation water that's already paid for.

Greywater systems save water and more. They can extend the life of a septic system, save time spent on watering, act as "drought insurance" (a source of irrigation during times of extreme water scarcity), and encourage the use of more environmentally friendly products. They also use less energy and fewer chemicals than other forms of wastewater treatment.

Water Savings from Greywater

You can expect to save between 10 and 20 gallons per person per day (or more) from a greywater system, though this number can fluctuate greatly. Studies estimate savings of between 16 and 40 percent of total household use. How much you actually save depends upon how much you currently irrigate, whether you use greywater on existing plants or you plant new ones, and how many greywater sources you can access. One study in Central California found an average household savings of 15,000 gallons per year after the grey­water system was installed (see Resources for more information). For tips on how to maximize water savings with your greywater system, see Maximize Your Water Savings.

Cost of Greywater Systems

Materials for simple greywater systems typically cost a few hundred dollars. If you're handy, you can install a system yourself in a day or two. Professional installations range from $700 to many thousands of dollars, depending on the type of system and your site. We'll discuss more details about specific system costs in chapter 6.

A Water-Efficient Home and Landscape

Before you start planning and constructing your greywater system, be sure to make your home and landscape as water-efficient as possible. Leaks waste an average of 14 percent of total home water use. Toilet and irrigation system leaks are often hidden and go undetected. A simple "mini makeover," such as switching out water-guzzling fixtures and appliances for efficient models, can lower total household water use by up to 35 percent.

Equally important is making your landscape water-smart. Plants that aren't able to be irrigated with greywater (or rainwater) should be those that are adapted to your local climate and are able to thrive without potable irrigation.

This book guides you through the design and installation of several types of greywater systems, but to maximize the full range of your water resources you'll also want to incorporate rainwater harvesting into your overall landscape design. See Resources for more information.

Types of Greywater Systems

There are many types of greywater systems, ranging from simply collecting water in buckets to fully automated irrigation systems. I'll group them according to their relative level of complexity and briefly explain how they work.

"Low-tech" systems for irrigation are the lowest in cost, simplest to install, and easiest to obtain permits for. Common types include laundry-to-landscape (L2L) and branched drain systems.

"Medium-tech" systems for irrigation incorporate a tank and pump to send greywater uphill or to pressurize it for drip irrigation.

"High-tech" systems are used for automated drip irrigation or toilet flushing in high-end residences and larger-scale commercial or multifamily buildings.

Hooray for the Washing Machine!

Washing machine water is typically the easiest source to reuse; you can direct greywater from the drain hose of the machine without cutting into the house's plumbing. A washing machine has an internal pump that automatically pumps out the water and can be used to direct greywater to the plants.

No-Fuss Gravity Systems from Showers and Baths

Showers and baths are excellent sources of greywater, though accessing the drainpipes may be challenging, depending on their location. A diverter valve placed in the drain line of the shower allows greywater to be diverted to the landscape. Gravity distribution systems are usually cheaper and require less maintenance than pumped systems, and distribute greywater through rigid drainage pipe. Greywater flow is divided into multiple irrigation lines to irrigate trees, bushes, vines, or larger perennials via mulch basins (see Mulch Basins).

Pros of Greywater Systems
  • Greywater is produced every day, all year long, and is a reliable source of irrigation.
  • Simple systems recycle tens of thousands of gallons a year for a relatively low cost.
  • Systems take up little space; often, all the pipes are buried and invisible.
  • It's easy to irrigate fruit trees, shrubs, and large annuals and perennials.
  • It's an automatic system, saving time and ensuring plants get watered.
  • It reduces wastewater going to the sewer or septic system.
Cons of Greywater Systems
  • Accessing greywater may be challenging, depending on how your house and landscape are designed.
  • Greywater reuse is not yet legal in some states.
  • Requires use of "plant-friendly" products in the house.
  • Small plants, or plants spread out over a large area, are more difficult to irrigate with the simplest systems, though pumped and filtered systems will work.

Pumped Systems: Filtered and Unfiltered

Pumped systems push greywater uphill or across long distances. Greywater is diverted into a surge tank, from which it's pumped to the landscape. Adding a filter allows grey­water to be distributed through smaller tubing, increasing the potential irrigation area but also increasing the cost and maintenance of the system.

Greywater Pioneer

Art Ludwig

Art Ludwig, affectionately called "The Greywater Guru" by many, is an ecological systems designer with 35 years of experience in the field.

He has studied and worked in 22 countries, authored the books Create an Oasis with Greywater (an excellent resource containing his decades of greywater experience) and Builder's Greywater Guide, and produced the "Laundry to Landscape" instructional video. He created the first plant and soil "biocompatible" laundry detergent, designed to break down into plant nutrients (see Resources). Art's most popular greywater inventions include the laundry-to-landscape and branched drain greywater systems. His policy work has greatly improved regulations in California, New Mexico, Arizona, and elsewhere.

What advice do you have for people wanting to install a greywater system?

Choose the simplest possible approach and implement it as well as possible.

What's your all-time favorite greywater system?

My favorite greywater system is my first branched drain system. I thought it would fail in a day, but it didn't. If fact, I couldn't get it to fail no matter what I did. Even after removing the screen in my kitchen sink and pushing compost scraps down the drain, the sink trap clogged daily, but everything that made it past the trap flowed out to the mulch basin via a free flow outlet, with no odors, no clogging, and no problems.

Greywater-irrigated landscape

Greywater or Graywater?

People often wonder why greywater is spelled two different ways. All around the world greywater is spelled with an "e," except by a few groups in the U.S., mostly regulators who write state codes (though some states, like Washington, use the "e" spelling). I like the "e" spelling to intentionally connect greywater to the global movement around water.

Health and Safety Considerations

A properly designed greywater system is safe for you and your family as well as the environment. As you design your system, keep the following considerations in mind:

  • Greywater is not safe to drink or ingest.
  • Greywater can harm aquatic ecosystems.
  • Avoid direct contact with greywater; your system should not create a puddle, pond, or any standing water, which creates a hazard to unsuspecting children and a place for mosquitoes to breed.
  • When watering food plants, don't let greywater contact edible portions of the food (to avoid direct ingestion). Don't irrigate root vegetables. Use subsurface irrigation for growing edibles near the ground.
  • Never use greywater in sprinklers where the spray could be breathed in.

Polluting Aquatic Ecosystems

The nutrients found in greywater are good for your garden but harmful to lakes, streams, and oceans. In the garden, the nutrients are fertilizer, sent to your plants each time you do laundry. If, instead of soaking into the soil, greywater runs into the storm drain and out to a river or bay, the nutrients pollute the water, feeding algae and robbing oxygen from aquatic organisms. This is similar to how the gigantic "dead zones" are created in our bays and oceans, usually by fertilizer runoff and sewer overflows. Don't let your greywater contribute!

Hazardous chemicals should never be used with a greywater system (or anywhere); they will contaminate your yard. When sent to the sewer plant they usually aren't removed either, and will end up in a river, lake, or ocean.

Is Greywater a Hazard to Your Health?

Some people hold the mistaken belief that greywater is hazardous, on par with sewage. There are many studies on the quality of greywater with respect to public health. Here are some key points:

  • Greywater is not safe to ingest. The quality is lower than drinking water quality. So don't drink greywater!
  • Greywater-irrigated soil is not safe to ingest, nor is soil irrigated with tap water. The City of Los Angeles conducted a study comparing greywater-irrigated soil and non-greywater-irrigated soil. Both were found to be unhealthy to ingest.
  • Many studies have found fecal indicator bacteria present, demonstrating the potential for greywater to contain fecally transmitted pathogens. A problem with using indicator bacteria, like fecal coliforms, is that the bacteria are present in all mammals' feces and can multiply on their own, resulting in inaccurate estimates of fecal matter in greywater. Other studies tested greywater for a cholesterol found only in the human gut, unable to grow on its own, and found the levels of feces reported in the other studies using indicator bacteria were 100 to 1,000 times too high. Does this matter? Some people still believe greywater isn't much cleaner than sewage and don't know that the methods used to test greywater were grossly inaccurate.
  • Few studies have found actual pathogens in greywater. Testing for specific pathogens is expensive, and pathogens are found only if someone in the home has the illness and germs get into the water. Some studies that tested for pathogens didn't find any, while others found common pathogens like Cryptosporidium spp. and Giardia spp., which are also found in most surface waters in the U.S. When people are sick they infect others by living together, directly touching, and sharing dishes; the risk of infection through a greywater system is extremely low.
  • There are no documented cases of illness resulting from greywater, while there are over three million documented cases of illness each year (just in the U.S.) from recreational contact with water contaminated by legal sewage treatment plants that overflow.

Is greywater hazardous to your health? No. Most likely greywater use improves public health by reducing waterborne illness since the only people potentially exposed already live together and greywater is kept out of sewer systems that often fail.

Greywater in Freezing Climates

Live somewhere chilly? Maintaining a greywater system in freezing conditions requires additional planning and precautions:

  • Gravity systems should drain completely. Standing water in the pipes could freeze and create a blockage, or potentially burst the pipe. Meticulously maintain proper slope throughout the entire system to ensure complete drainage.
  • Do not allow any standing water in lines from pumped systems. Ensure greywater will drain out or drain back into the tank.
  • In a pumped or L2L system: If it's logistically difficult to prevent standing water in the line, create an automatic bypass at the beginning of the system. If the main line freezes, water will be forced out the bypass; for example, a tee fitting with a tube running high enough up so greywater doesn't exit unless the line is blocked (if the tube is too short, greywater will come out like a fountain).
  • Greenhouses irrigated by greywater (see Greywater for Greenhouses) can produce food and greenery all year long.
  • Shut off the system (and drain down any places with standing water) until irrigation is needed. Install a drain-down valve at the low point of the system to empty the pipes for winter. Use a tee with a ball valve at the lowest point. Close the valve when using the system and open it to drain the line. Note: Shutting off the system may be unnecessary, even with freezing, snowy weather. The warmth in greywater can keep lines open and the ground biologically active (see Cold-Climate Greywater: Evergreen Lodge below).
  • Consider a toilet-flushing system if there is no irrigation need. (See Using Greywater Indoors: Toilet Flushing.)

    With proper design and installation, greywater can be used fully in freezing climates.

Cold-Climate Greywater

Evergreen Lodge

Evergreen Lodge (see Resources), in the mountains of Yosemite, California, recycles nearly two million gallons of water annually, thanks to the work of Regina Hirsch of Sierra Watershed Progressive and the lodge's environmentally conscious leadership.

Over the past few years, Regina and her crew installed dozens of systems at the lodge, both simple gravity-fed branched drain systems (in 55 guest cabins) and large automated systems from the commercial laundry and staff dorms.

"The system is a big win for the lodge," reflects owner Brian Anderluh. "We were able to take greywater out of our septic system and use it instead for our landscape beautification project, without requiring any more fresh water from our well."


  • “Simple, affordable projects and strategies to conserve water and reuse it for household food gardens, groundwater recharge, and soil regeneration. These solutions are a win for the household and for the environment.” — Gemma Bulos, director of Global Women’s Water Initiative

    “Practical guidance for conserving and efficiently using our precious water. This comprehensive book explores every detail of how to capture and reuse greywater to create lush landscapes.” — Paula Kehoe, director of water resources at the San Francisco Public Utilities Commission

On Sale
Apr 4, 2017
Page Count
200 pages

Laura Allen

Laura Allen

About the Author

Laura Allen is the author of The Water-Wise Home and cofounder of Greywater Action, a collaborative of educators who teach residents and tradespeople about affordable and simple household water systems that dramatically reduce water use and foster sustainable cultures of water. She leads classes and workshops, including the first training program for professional greywater installers, and participates in writing state government greywater and composting toilet codes. She lives in Eugene, Oregon.

Learn more about this author