Local lifestyle columnists

What you should know about ‘graywater’ and your garden

By From page D4 | March 30, 2014

During drought years, interest in the use of graywater resurfaces. The use of graywater around your home can help conserve clean potable water you would normally use in your yard. But it could potentially harm your yard as well.

What is graywater?

The California Health and Safety Code (section 17922.12) defines graywater as “untreated wastewater that has not been contaminated by any toilet discharge, has not been affected by any infectious, contaminated or unhealthy bodily wastes and does not present a threat from contamination by unhealthful processing, manufacturing, or operating wastes. ‘Graywater’ includes but is not limited to wastewater from bathtubs, showers, bathroom wash basins, clothes washing machines and laundry tubs, but does not include wastewater from kitchen sinks or dishwashers.” Water used from laundering diapers, greasy clothes or clothes contaminated with automotive fluids is considered blackwater, not graywater, and should not be used.

Good or bad for your lawn and garden?

Graywater can be used to keep your lawn, shrubbery and trees alive in the absence of clean water. But the answer as to whether or not it is good for your specific greenery depends upon factors such as the type of greenery you intend to use it to irrigate, the specific soaps and detergent you use, your soil, and your irrigation method. Let’s look at the important role of soaps and detergents.

The composition of your graywater depends upon what goes into it. Your laundry detergent and soaps contain elements that may be either harmful, or helpful to the greenery you intend to irrigate with the graywater. Detergents often contain alkyl benzene, bleach, borax, chlorine, and sodium that should be avoided in your graywater. But if you grab your laundry detergent container, it may not list all its ingredients so you may not know what’s in it.

The reason it’s important for you to know is that high sodium, calcium or potassium levels resulting from your detergent can have a negative effect on our poorly drained clay soil and your greenery. Too much chlorine or sodium can cause leaf burn and other problems, and too much boron can be toxic to plants. Some plants that do not tolerate high sodium levels include crape myrtles and holly; plus azaleas, camellias, gardenias, and hydrangeas do not do well with the alkalinity of graywater.

The Graywater Guide issued by the California Department of Water Resources does not recommend the use of graywater for vegetables and other edible plants. For your health, you should not come into direct contact with graywater. The reason is because graywater can contain bacteria or viruses harmful to your health.

Many plants and grasses grow well with irrigation from graywater. Basically you need to determine whether the specific greenery in your yard will benefit you’re your specific graywater. This involves finding out the specific needs and vulnerabilities of the plants, shrubs, trees and other greenery in your yard. You also need to consider whether or not your household is willing to change to a more graywater friendly soap and detergent brands if necessary, if you decide to use graywater.

Graywater irrigation systems

Whether or not a permit is required to install a graywater irrigation system depends on several factors. The Solano County website, www.solanocounty.com/depts/rm/environmental_health/technical/well_n_on_site_sewage_disposal_program/default.asp, provides information on the permit requirements.

Some homeowners who don’t want to go to the expense of having a system installed may be thinking of collecting graywater by redirecting their clothes washing machine graywater into buckets rather than allowing it to drain down their laundry room basin. Again, because of the potential of the graywater coming in contact with your skin, this is not recommended.

If you want to learn more about graywater, or are considering installing a graywater system, be sure to check out the following documents and information.

Kathy Low is a Master Gardener with the University of California Cooperative Extension office in Fairfield. If you have gardening questions, call the Master Gardener’s office at 784-1322.


Using graywater in your home landscape

Graywater Guide: www.water.ca.gov/wateruseefficiency/docs/graywater_guide_book.pdf

Safe Use of Household Graywater: http://aces.nmsu.edu/pubs/_m/m-106.html

Using Gray Water at Home: www.azdeq.gov/environ/water/permits/download/graybro.pdf

Greywater Systems- Benefits, Drawbacks and Uses of Greywater: http://extension.ucdavis.edu/unit/green_building_and_sustainability/pdf/resources/greywater.pdf

Graywater Regulations: www.solanocounty.com/civicax/filebank/blobdload.aspx?blobid=13396

Kathy Low


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