Is this the year to plan for gray water use in your garden?

Water is a precious resource; conserving it is a key to Earth-friendly gardening.

We have been blessed with abundant rainfall, magnificent waterfalls and fast-moving creeks this past winter. But where is all that flowing water heading? Unfortunately, not into more reservoirs or water storage facilities. The reality is that we still need to think about water and using our resources wisely.

Gray water has been discussed widely during our long drought years. Is this the year to plan for gray water use in your garden? If the thought of a future drought is not a motivator, how about the increasing cost of Marin Municipal water?

Some people seem to be a bit squeamish about the concept of watering the garden with “dirty” water. A clear definition of what is considered gray water is found in “Shades of Graywater,” an informative brochure compiled by Marin Master Gardeners.

Gray water is untreated wastewater collected from bathtubs, showers, washing machines and bathroom sinks, and reused for outdoor irrigation or toilet flushing.

Dark gray water is water from kitchen sinks and dishwashers that may have a high content of organic matter, encouraging bacterial growth.

Black water is toilet wastewater or water that has touched soiled diapers. Neither dark gray water nor black water is allowed to be reused in landscape irrigation.

Installing your simple home graywater laundry-to-landscape (L2L) system requires no permits. This system uses discharge water only from a single domestic clothes washing machine in a one- or two-family dwelling that distributes it to the yard for subsurface irrigation of landscape plants. These DIY systems are generally the easiest and least expensive ways to make graywater usable in your landscape.

Some basic usage guidelines:

• Gray water is to be used on ornamental shrubs, fruit trees and edibles that do not reach the ground.

• Use only biodegradable, pH-balanced and sodium, boron and chlorine-free laundry products.

• Rinse cycle water is preferable to wash cycle discharge.

• Don’t irrigate leafy greens or root vegetables with graywater.

• Watering a lawn is not the best use of gray water.

• The irrigation area should be downhill from the clothes washing machine.

• Gray water must be discharged into the soil under 2 inches of cover material.

• Gray water is not to be used in spray irrigation or allowed to pool or run off the owner’s property.

• Don’t discharge gray water near a freshwater source.

• Alternate gray water irrigation with fresh water to minimize salt buildup.

• Avoid human and pet contact with gray water to minimize potential health risks.

• More complex gray water systems that discharge more than 250 gallons per day and may also involve pumps, tanks and filtration systems may require one or more permits.

Information for the do-it-yourselfer, as well as resources for professional designers and installers, can all be found at marinmg.ucanr.edu/BASICS/CONSERVE_WATER_-_ENERGY/Graywater. This page also includes links to a L2L pamphlet and extensive information from the County of Marin. Included on the county’s website are FAQs and lists of specific plants that do and don’t benefit from graywater irrigation.

With as much as 30% to 50% of residential water usage producing gray water, any reuse is a helpful savings of our precious drinking water. If laundry-to-landscape is just not for you, put a bucket in your shower to collect water as it warms to your liking and use this water to flush your toilet — simple, easy, anyone can do it graywater usage.

Gray water use is not only a water-saving practice. Transporting clean potable water from the source to your home is an expensive use of energy. Reusing water that is already in your dwelling can result in both water and energy savings: a double win for both you and Mother Earth!

Sponsored by UC Cooperative Extension, the University of California Marin Master Gardeners provides science- and research-based information for Marin home gardeners.  Email questions to helpdesk@marinmg.org. Attach photos for inquiries about plant pests or diseases. Please call 415-473-4910 to see when a master gardener will be at the office or drop off samples 24/7 in the sample box outside the office. To attend a gardening workshop or subscribe to Leaflet, a free quarterly e-newsletter, go to marinmg.ucanr.edu.