These days, more and more gardeners are turning to greywater to provide their landscape with needed moisture.
It’s a frugal practice that can save scarce fresh water supplies, especially during drought conditions.
Graywater is all the non-toilet wastewater produced by the average household. This includes bath water and dish water from sinks, as well as water from washing machines, showers and dishwashers. I also include water from the ice left over after a beverage is finished, and water that might have been sitting on your night stand overnight. Don’t laugh. Since my husband and I both need a sip of water during the night and take a small glass with us to bed, collecting that “used” water gives me enough each week to water most of my indoor plants. It’s only a few tablespoons at a time, but it adds up. And remember that houseplants need only a small amount of moisture a day to thrive.
Sounds gross. Is graywater safe?
Although gray water does not need extensive chemical or biological treatment before it can be used in the garden as irrigation water, it still must be used carefully because it can contain things like grease, hair, detergent, cosmetics, dead skin, and food particles. One recommendation, from the University of Massachusetts, is to apply no more than a 1/2 gallon of greywater per square foot of soil. So, if you have a 200 square foot landscape area, use no more than 100 gallons of greywater per week.
According to the Colorado State University Extension, the greatest danger in using gray water is the build-up of sodium in the soil. Most cleaning agents contain sodium salts which can damage the soil structure and create an alkaline condition if used over a long period of time. So, if you use graywater regularly, you might want to have your soil tested periodically to make sure the pH is not above 7.5.
Soaps and detergents are biodegradable, but they can also present problems when graywater is used over an extended period. Rotate graywater applications with rainfall or fresh water to keep salts from building up within the soil.
How do I collect graywater?
One obstacle to overcome is the collection of graywater in the first place. You can use some kind of a scooper to remove dish water and bath water to fill a bucket or pail, or remove the drain trap to allow for the water to flow into a bucket placed directly under your sink or tub. This is also probably the easiest way to transport your graywater to your garden.
But for the collection of shower, washing machine and dishwasher graywater, you’ll need to make adjustments to your drainage system to allow for collection.
You can find some helpful tips for fitting your house with a graywater collection system, and mistakes to avoid at Oasis Design. Be sure and check with the local health department about health codes in your area before before making any plumbing changes.
A few tips for using graywater
- Apply greywater directly to the ground surface. Do not apply on leaves or other parts of the plants
- Some experts suggest using graywater only on ornamental landscapes, and not in the vegetable garden.
- If you need to use graywater for irrigating food plants, restrict its application to the soil around plants such as corn, tomatoes, broccoli, or other vegetables of which only the above ground part is eaten. Never apply graywater to leafy vegetables or root crops.
- Using compost mulches will help decompose contaminants in greywater more quickly.
- Use gray water only on well-established plants. Seedlings can’t withstand the impurities of the waste water.
- Untreated greywater should not be kept for longer than one day. But by adding two tablespoons of chlorine bleach per gallon of water, you can keep your graywater a little longer.
- DO NOT drink greywater.
- DO NOT use greywater in your sprinkler system, or use greywater to wash patios, walkways or driveways.
Conserving our water resources is important. By using water wisely now, you help to ensure that there will be enough water for everyone in the future.