Gardening with Greywater
Limited access to clean water is a global crisis, so it seems almost criminal to use pure clean water for our suburban landscapes. Getting rid of, or minimizing lawns helps in reducing water use, but we can go further by recycling greywater from our homes to water our gardens.
But I’ll say upfront that greywater is NOT recommend for watering your vegetables and other edibles, except for fruit trees. By using greywater for the non-edible, ornamental parts of your landscape you can conserve significant amounts of fresh water.
Most likely, not all of your landscaping is devoted to growing vegetables or fruit, so it is recommended as a preferred practice that you use greywater on everything but the edibles (except fruit trees), then use fresh water for your veggie garden. Greywater is safe for watering fruit trees if it is delivered underground, but it is considered unsafe for any other edibles because of the risk of bacterial contamination.
The California Department of Housing and Community Development (HDC), estimates that as much as one-third of home water use goes to landscaping (watering lawns, trees and gardens). And according to Forrest Linebarger, of Vox Design Group, 25% of California’s energy is spent on pumping water to and from homes and industries. He feels that recycling the waste water from homes on site is an obvious solution, and in fact that it’s madness not to do so.
What is Greywater?
Greywater is the water from your kitchen sink, dishwasher, washing machine, and bathroom sinks- anything but the toilets (blackwater). Of course the quality of different waste streams will be variable, depending on the types of cleaning products you use, and they may have an impact on your soil. In California, water from the kitchen sink is not allowed for watering your garden. It is loaded with food particles that have to be broken down, and a hot bed for bacteria.
What to Consider When Using Greywater for Your Garden
Greywater typically contains oils, fats, detergents, soaps, nutrients, salts and particles of food (if kitchen waste water is included), hair, and lint. It is mostly alkaline and can be high in salts, due to the cleaning products used in dish and clothes washing machines. The alkaline nature of waste water with detergents may change the pH of the soil over time. Most people that route greywater to their gardens use biodegradable detergents so that harmful chemicals are not a concern.
As mentioned, water from the kitchen sink that is unfiltered contains fats and food that have to be digested. As a friend of mine commented, it’s like raw compost material that still has to be processed. It’s simpler not to use kitchen waste water for this reason.
Linebarger’s company designs and installs greywater systems and in his experience the quality of residential waste water is not a big concern (he’s located in California, so he’s not dealing with the issues of kitchen water). In our phone conversation he explained that Vox uses gravel and mulch basins in their systems to disperse the greywater going into the landscape so that it’s not concentrated in one area.
The video above shows the system he designed for a home that waters fruit trees with greywater. Concerns about bad effects on the soil and plants may are more likely if your greywater is being directly dispensed into a closed container, such as a planter. He considers that a laundry greywater system is the simplest: the parts may cost about $400, it could be installed in a weekend, and it doesn’t require a permit. Such a system would reuse on average 5,000 -7,000 gallons of water a year. An average household might use about 85,000 gallons of water a year that could be diverted to greywater, and just about equals what the average suburban lot needs to water its landscaping.
Basic Guidelines For Using Greywater
- Don’t apply as a mist (aerosol), deliver directly to soil, preferably underground
- Don’t apply to crops, except fruit trees
- Don’t apply where runoff into a waterway is a concern
- Don’t store it (risk of bacterial growth)
For more information on greywater polices nationally, see the Oasis Designs web site.
Photo: Urban Artichoke