What is Greywater?

Keep your lawn and garden lush without wasting resources by capturing and recycling the greywater that drains from your sink, shower, and washing machine.

| January 2018

  • You can identify greywater sources in your home, estimate flow rate, and pinpoint where to redirect the wastewater for the greatest benefit.
    Photo by Pixabay/Kaboompics
  • “Greywater, Green Landscape” by Laura Allen explains the benefits of reusing water from your home to save money and resources.
    Cover courtesy Storey Publishing

Greywater, Green Landscape by Laura Allen (Storey Publishing, 2017) is an accessible and detailed guide that walks you through each step of planning and installing a variety of greywater systems, including laundry-to-landscape and branched drain gravity-fed systems. This excerpt explains the basic concepts of greywater.

You can purchase this book in the Mother Earth Living store: Greywater, Green Landscape.

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 grey-water system was installed.

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.

Types of Greywater Systems

There are many types of greywater systems, ranging from simply collecting water in buckets to fully automated irrigation systems.“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.

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 grey-water to be distributed through smaller tubing, increasing the potential irrigation area but also increasing the cost and maintenance of the system.

Greywater in Freezing Climates

Live somewhere chilly? Maintaining a grey-water system in freezing conditions requires additional planning and precautions.

Gravity systems should drain completely. Standing water in the pipes could freeze and create a block-age, 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). 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. Consider a toilet-flushing system if there is no irrigation need.




Excerpted from Greywater, Green Landscape by Laura Allen, used with permission from Storey Publishing. Buy this book from the Mother Earth Living store: Greywater.






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