by Scott Loosley
QI am writing to inquire about the use of gray water for landscape irrigation. I have heard it's illegal to use gray water for irrigation in some cities. How can I use gray water for my landscape, and is it possible to do it within city codes? AThe term "gray water" hasn't been mentioned as much in the last two years, but if we have another dry winter, it may be the best irrigation source to keep your landscape alive. "Gray water" is a term used to identify types of household wash water that has not come in contact with toilet waste, such as water from bathtubs, showers, bathroom wash basins, clothes washing machines and laundry tubs. These can all be used as sources of irrigation water for your landscape if common sense and care are used.
Since the sources of gray water have the potential for residues that may contain bacteria and viruses, public health officials have prohibited their use for surface irrigation. This is why some municipalities have not actively promoted the conversion of landscape irrigation for gray water use.
However, the law does allow the use of gray water for irrigation under the California Plumbing Code, Title 24, Part 5, of the California Administrative Code. The entry is listed as Appendix J, Graywater Systems For Single Family Dwellings.
The law allowing for gray water use was authored by local Assemblyman Byron Sher and was signed by Gov. Pete Wilson in July 1992. It directed both the California Department of Water Resources and the California Department of Health Services to co-publish standards for the use of gray water for irrigation. In March of this year, Appendix J was formally adopted into the California Plumbing code by the California Building Standards Commission and became law on Nov. 7, 1994.
The law is specific about the installation and use of gray water.
The systems can only be used for single-family dwellings and may only be used for subsurface irrigation.
Contact with gray water by humans is prohibited and it cannot be used to irrigate vegetable gardens.
Also, permits are needed before constructing or modifying gray water systems. Although efficient, these systems can be expensive to install, costing $2,000 or more. Construction includes diverting gray water from sources in the house into a holding tank where it is then pumped or gravity-fed into a system of underground perforated pipe. The system should eventually pay for itself since there would be less expense for irrigation water.
The use of gray water for irrigation requires more care when choosing products that you use in your home. If you have a water softener, it must be turned off when using the water for plants. Softened water contains more sodium than normal tap water. If used over a long period of time, the sodium can cause the soil to become "tighter," resisting water penetration. Also, some laundry products can be harmful to plants. Chlorine bleach or detergents that contain boron should be avoided. Often, damage to plants appears as a burning of the leaf edges. Some plants may be more sensitive than others.
For more information about this topic, you may want to read "Graywater Use in the Landscape: How to Use Graywater to Save Your Landscape During Droughts," by Robert Kourik. Or contact Stephen Bilson of ReWater Systems, Inc. of Palo Alto at 324-1307.
QI planted a perennial border a year ago and have enjoyed it all summer. I have heard that I should cut back my perennials, but I'm not sure when I should do it. When is the best time to cut back my perennials? AMost herbaceous perennials begin blooming in spring and put on a show of blossoms through the summer. The only pruning they need during that growing period is to cut off the spent blossoms as they occur. This allows the plant to direct its energy to producing more bloom instead of producing seed. As autumn approaches, some plants start to go dormant and foliage begins to dry and turn brown. The "tidy" gardener cuts back this unsightly foliage and has a perennial garden with a well-kept look.
There are some perennials that refuse to quit blooming. They keep pushing out blossoms until the first heavy frost. It would not be wise to cut back these active perennials if there is a chance they could be damaged by a hard freeze. In this situation, it's better to wait until the danger of a freeze has passed, usually around the President's Day in February.
This is also a good time for the less tidy gardener to cut back all those perennials that could have been attended to in the fall. One of the advantages of cutting back dead foliage in the fall is to eliminate diseased growth and hiding places for insects, snails and slugs.
Either time, late fall or early spring, is an appropriate time to cut back herbaceous perennials.
Scott Loosley is the horticulturist at the Gamble Garden Center in Palo Alto. His column appears the third Friday of the month. Send questions to Loosley care of Palo Alto Weekly, P.O. Box 1610, Palo Alto, CA 94302.
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