- Author: Help Desk Team
Q: Can I use the graywater from my washing machine to water my vegetable garden and fruit trees?
A: There are two key considerations, discussed below, relating to the use of graywater in the garden: what is meant by the term graywater and on what plants to use it.
Graywater Definition
Graywater is untreated, non-disinfected household wastewater that does not include toilet waste. It may be sourced from showers, baths, and washing machines. Untreated water from sources such as kitchen sinks and dishwashers, which may have properties that encourage pathogens, is called dark graywater. Water from toilets and washing machines used to launder diapers or chemically contaminated clothing is called black water. Only graywater should be used in the landscape.
Graywater Usage
Graywater can be safely used to water landscape plants and orchard trees. Because graywater can contain bacteria and viruses that cause illness, it should not be used to grow vegetables if the edible portion may come in contact with the soil. For example, graywater should not be used for growing asparagus, beets, carrots, cucumbers, lettuces and other salad greens, garlic, onions, potatoes, melons, squash, bush beans, radishes, turnips, unstaked tomatoes, or strawberries. Crops not touching the ground like staked tomatoes, peppers, and eggplants should be OK.
https://ccmg.ucanr.edu/files/289340.pdf
Laundry Detergent Considerations
When using laundry rinse water to irrigate plants, your choice of household products will affect the composition of the graywater. The wrong products can adversely affect plants and soils. It is best to avoid using products that contain sodium or sodium compounds, bleach, or boron, as these can result in an alkaline soil condition that suppresses healthy soil biologic activity and is poorly tolerated by many plants.
Although the UC Master Gardener Program of Contra Costa County cannot recommend any products, the FAQ page on Greywater Action's website (https://greywateraction.org/greywater-faq/) lists some products that are plant friendly. These are generally biodegradable, non-toxic, and salt and boron free. The Ecology Center in Berkeley has also evaluated several cleaning products for compatibility with graywater systems. Consult their website at https://ecologycenter.org/factsheets/ for a current list of products. (Click on the link to Greywater-Compatible Cleaning Products.)
Other Considerations
Some key takeaways excerpted from our Marin Master Gardener colleagues are listed below. https://marinmg.ucanr.edu/BASICS/CONSERVE_WATER_-_ENERGY/Graywater/
Do:
Water ornamentals with graywater which is often rich in nutrients.
Check your plants first—Acid-loving plants won't tolerate salts found in high pH graywater and evergreen trees are often more salt-sensitive than deciduous trees.
Alternate graywater irrigation with fresh water to minimize salt build up.
Watch what you put in the wash. Use biodegradable pH balanced, sodium-free, boron-free, chlorine-free products in the washing machine and for bathing.
Apply graywater directly to the ground—don't allow it to be sprayed on plant surfaces.
Use graywater within 24 hours after collecting to minimize bacterial growth.
Don't:
Don't let graywater come in contact with skin.
Don't use on root vegetables such as carrots and onions.
Don't use on lawns unless the graywater is delivered below the surface. If sprayed on the surface, people or pets may come in contact with it.
I hope this helps. Please don't hesitate to contact us with any further questions. Good luck with your tomatoes and fruit trees!
Help Desk of the UC Master Gardeners of Contra Costa County (GD)
Steele, a UC Master Gardener in Orange County since 2000, brought in a contractor to install a valve behind her washing machine and flexible tubing to channel graywater to mulch pits in the front yard. The pits ensure that there is no graywater runoff or pooling on the property, important factors for using the recycled water. Steele found that the pits also work well for distributing fertilizer to her plants.
“I feel very positively about it,” Steele said. “One of my rose bushes, a climbing Fourth of July, is happier than it's ever been.”
With recent changes in state regulations, residents of single-family and two-family homes in most California communities may install simple laundry-to-landscape graywater systems without a permit, said Janet Hartin, UC Agriculture and Natural Resources (UC ANR) environmental horticulture advisor.
“On average, 10 to 25 gallons of water is generated per load in a front-loading washer and about 40 gallons per load from a top loader,” said Hartin, a horticulturist with UC ANR Cooperative Extension in San Bernardino, Los Angeles and Riverside counties. “A family of four running about eight loads of wash per week can keep three to six mature trees well irrigated just with laundry water.”
Hartin and co-author Ben Faber, a UC ANR Cooperative Extension advisor in Ventura County, recently published a 10-page guideline that details the basics of developing a laundry-to-landscape graywater use system in California. The publication, Use of Graywater in Urban Landscapes in California, can be downloaded for free from the UC ANR online publications catalog.
Hartin and Faber's publication focuses on washing machine water because, among the legal sources of graywater – including bathtubs, showers, bathroom washbasins and laundry tubs – regulations pertaining to its use have been eased at the state level. State health codes preclude the use of toilet discharge (‘black water') and wastewater from kitchen sinks or dishwashers in order to prevent the spread of pathogens in the landscape. Safe use of laundry graywater still requires precautions to maintain food safety and prevent pollution.
Hartin recommends laundry graywater users carefully select their laundry detergent to make sure it does not contain boron, phosphates or bleach.
“Choose liquid detergents over powders to avoid potentially high levels of sodium and fillers containing sodium which can have a negative impact on plants,” Hartin said. “Products such as Borax that contain boron can also prove toxic to plants. Although boron is required for plant growth, it is needed in very small amounts. Also, instead of using chlorine-containing bleach, use oxygenated bleaches like hydrogen peroxide.”
Laundering cloth diapers or other similarly soiled items should be done with the washing machine draining into the sewer, not the graywater system.
“The first concern should be making sure pathogens are not transferred onto humans or food for human consumption,” she said.
The recycled water can be used to irrigate trees, shrubs and flowers, but not root vegetables or in any capacity where it might touch edible leaves or fruit. To be on the safe side, Hartin recommends using potable water for all edible crops and using recycled graywater for ornamental plants.
An initiative to improve California water quality, quantity and security is part of the UC Division of Agriculture and Natural Resources Strategic Vision 2025.
Author: Jeannette E. Warnert
- Author: Janet Hartin
California is in the midst of the worst drought in decades. But you can save your valued trees and landscape plants by following a few simple principles. Watering mature trees deeply just once during mid-summer will keep most species alive, especially if there is a three inch layer of mulch on the top of the soil to keep evaporation down. Be sure to water outward toward the dripline of the tree rather than near the trunk. Keep weeds out of your garden; they will win the water fight. Don't fertilize your landscape during the drought and avoid ripping out your current landscape in the middle of summer to replace it with a drought tolerant one; young plants require more water than established landscapes, and more frequent irrigations. For more information on how to reduce water use in your landscape and garden and to learn more about using graywater from your washing machine to irrigate your landscape click on this link. http://cesanbernardino.ucanr.edu/Drought_Resources/ Janet Hartin, Environmental Horticulture Advisor, University of California ANR Cooperative Extension, San Bernardino, Riverside, and Los Angeles Counties.
- Author: Gerry L Hernandez
50 Shades of Graywater
I have done a little research on graywater and like the movie; there are many shades of gray we are not familiar with. I am going to write about the basics of graywater usage. I think there are easier ways to save water than using graywater but if you would like to look into it here are the basics.
What is graywater?
Graywater is untreated wastewater collected from bathtubs, showers, washing machines and bathroom sinks and reused for outdoor irrigation or toilet flushing. It does not include wastewater from kitchen sinks or dishwashers. Of course, it does not include toilet water.
Is graywater allowed in my area and do I need a permit?
Current California law (as of January 1, 2014) graywater is legal but laws can change. A permit is not needed for simple clothes washing system.
Simple systems
Simple systems can include buckets of water collected from warming up the shower water. Just be sure to use the water within 24 hours of collection. In 2009 California declared it legal to divert washing machine water to home gardens. This is the easiest way to use graywater and does not need a permit.
Where do I use graywater?
Graywater should only be used on ornamental plants. It should not be used on edible plants. Use graywater friendly soaps, shampoos and detergents. The quality of your graywater depends upon what goes into it.
Benefits of graywater
Using a graywater system to irrigate landscape plants can conserve water by recycling water otherwise destined for a treatment plant. Most graywater systems will not supply enough water to irrigate the entire yard but it can supplement your irrigation.
Risks and problems of graywater
There has been limited research on the risks of graywater. Here are some possible risks.
- Can have pathogens such as E. coli, salmonella.
- Can contain, bleach, boron, salts.
- Cannot store it over 24 hours.
- Clogs drip systems.
- Don't use near a creek or river.
- Don't let it run off your property.
- Need to use a mulch basin.
- Don't use on acid loving plants.
- Don't use on your lawn.
There are many resources for graywater on the internet. Please be careful what resources you use. I used resources from the University of California, several UC Master Gardener programs and Sunset.
Help From the Contra Costa Master Gardeners' Help Desk
Request: I'd like to reduce the use of tap water to irrigate my garden by recycling water from our washing machine. I understand this recycle/reuse water is called "graywater". Could you provide me some guidance on how to use graywater for my garden?
Response: Thank you for contracting Master Gardeners' Help Desk about using graywater in your garden. It's important that we learn how to use water more efficiently as drought conditions continue. I applaud your desire to use graywater as a tool to optimize our finite water resources. However, the use of graywater does come with some challenges.
Graywater is untreated waste water from clothes washers, showers, bathtubs, bathroom sinks and laundry tubs that is used for outdoor watering. In California, graywater does not include waste water from kitchen sinks, dishwashers, toilets, or laundry water from soiled diapers.
for a washing machine
Graywater is also an option for irrigating your ornamentals but it should not be used to water root vegetables or any vegetables whose plant parts come into contact with the soil due to the potential that human pathogens might be present.
For more information on graywater installations, see the East Bay Municipal Utility District website http://www.ebmud.com/sites/default/files/pdfs/Graywater%20Fact%20Sheet.pdf and
https://www.ebmud.com/water-and-wastewater/water-conservation/watersmart-gardener.
When using graywater to irrigate plants, you should avoid using household products that contain sodium or sodium compounds, bleach or boron, as these can adversely affect plants and soils resulting in an alkaline soils condition not well tolerated by many plants. The UC article "Using Household Wastewater on Plants" http://vric.ucdavis.edu/pdf/fertilization_Householdwastewater.pdf describes the effect on plants of using products which contain boron and chlorine. The Greywater Action website http://greywateraction.org/contentgreywater?friendly?products/ provides a list of products available that are phosphate, sodium, chlorine and boron free. Although we can't recommend any specific brand, Greywater Action considers the following laundry products graywater friendly: Oasis Liquid Laundry Detergent, ECOS liquid detergent, Vaska and Dr. Bronners liquid soap. The Ecology Center in Berkeley also evaluated a number of laundry products for compatibility with graywater systems and the results are listed on their website: http://ecologycenter.org/factsheets/greywater?cleaning?products/ .
I hope this is helpful. Please feel free to contact us if you have any additional questions.
Thank you for doing your part to conserve water.
Contra Costa Master Gardeners' Help Desk
Note: The Contra Costa Master Gardener Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/
