Through the natural water cycle, the Earth has recycled and reused water for millions of years. Reusing greywater for irrigation reconnects urban residents and our backyard gardens to the natural water cycle.
What is greywater?
Greywater is gently used water coming from sinks, showers, baths, and washing machines. Greywater is never from toilets or laundry water washing diapers. In California kitchen sink water is not currently considered greywater.
Why use greywater?
Plants don’t need clean drinking water to thrive! Using greywater for irrigation saves water and reduces the energy, chemicals, and costs involved in treating water to potable quality. Greywater systems can also extend the life of a septic system, save time spent on watering, be a source of water during extreme drought, and encourage the use of more environmentally friendly products. They also use less energy and fewer chemicals than other forms of wastewater treatment.
- Reduced fresh water use
- Money saved on water bills or well pump use
- Less energy & chemical use
- Less strain on waste water treatment systems (septic / sewer)
- Groundwater recharge
- Free nutrients to fertilize plants
- Increased awareness of WATER
How much water will I save?
You can expect to save between 10 and 20 gallons per person per day (or more) from a properly designed greywater system. Studies estimate savings of between 16 and 40 percent of total household use. Your actual savings depends on 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.
Water & Greywater Facts
- The average person in the U.S. uses ~100 gallons of fresh water every day.
- Roughly 1/3 to 1/2 of this fresh water is used in the landscape.
- Dish, shower, and laundry water comprise 50-80% of residential “waste” water. This water can, and should be, reused for other purposes such as landscape irrigation.
- Reusing greywater can save ~36,000 gallons of fresh water per year per family.
Are greywater systems legal?
Yes, greywater systems are legal in California and are regulated by the state plumbing code. Some systems that do not alter the household plumbing don’t require a permit if basic guidelines are followed, while most others do require permits. See http://greywateraction.org/greywater-codes-and-policy/ for more info.
How can you use greywater?
There are many types of greywater systems, ranging from manually collecting water in buckets to fully automated irrigation systems. Some of the most popular, simple, and affordable greywater irrigation systems include the laundry-to-landscape (L2L) and branched-drain systems. Other systems use pumps to send greywater uphill or to pressurize it for drip irrigation (with manually cleaned filters). There are also sophisticated “high-tech” systems that provide automated drip irrigation with self-cleaning filters in high-end residential houses and larger-scale commercial or multifamily buildings.
Greywater can also be used to flush toilets, however, it’s typically cheaper and easier to set up an outdoor greywater irrigation system. If your site doesn’t need irrigation, there are systems that treat greywater for use in flushing the toilet but require permits and proper maintenance.
Laundry to Landscape (L2L) Greywater
- Legal to install in CA without a permit (in several cities, like Chico) so long as state guidelines are followed
- Accessible 3-way valve makes it easy to switch between the greywater system and the sewer/septic
- Greywater can travel slightly uphill (think small bumps in your yard) or longer distances across flat yards
- Little digging required to install and very little maintenance after installation
- Easy to spread out water and reach many plants (up to 20 with a top-loading machine, up to 8 with a front-loading machine, up to 10 with a top-efficient machine)
- Flexible- easy to change after installation
- Involves some very minor plumbing rerouting (without cutting into existing plumbing)
- If poorly designed the system could add strain on washer pump and potentially shorten its life
- Some parts not readily available and must be ordered (e.g. 3-Way valve and Auto Vent)