Watering Gardens with Gray Water

Watering the garden and lawn with a sprinkler hooked up to municipal water sources is fine in non-drought conditions. If a water ban has been issued, however, a different means of moisture for your lawn and garden may be necessary.

One method is to use waste water, also known as gray water, which is generated in your household. Following are the basics of gray water and how to use it in your home garden.

What is Gray Water?

Gray water is the waste water produced in a household, such as the water from bathtubs, showers, sinks, washing machines and dishwashers. It should not include kitchen water that may contain animal waste, grease or fats; toilet water; or washing machine water that may contain fecal matter or bacteria, such as from washing diapers. If you must use water from the kitchen sink and dishwasher, try to limit the amount of grease and solid food particles that are washed down the drain.

How Much Gray Water Can I Use in My Garden?

Gray water usually contains grease, hair, detergent, cosmetics, dead skin, food particles and small amounts of fecal matter, so it should used carefully. Approximately one square foot of well-drained soil can take about a half gallon of gray water per week. Be sure to alternate watering your garden with gray water and with fresh water to help rid the soil of any contaminants that may be present.

Aren’t Soaps and Detergents Harmful to the Soil and to Plants?

Soaps and detergents are biodegradable, but can pose problems in areas when gray water is used over a long period. Most cleaning agents contain sodium salts, which, in excessive amounts, can damage the soil structure and plants, as well as create an alkaline condition.

Detergents with "softening power" should not be used in your recycled water – they will contain large amounts of sodium-based compounds. The phosphates that are present in detergents can be good for plant growth; however, the detergents highest in phosphates usually contain the most sodium. If you are planning to use washing machine water to water your plants, limit the amount of bleach you use, and do not use detergents containing boron, which is toxic to plants.

How Should Gray Water Be Applied?

Follow these guidelines for safe use of gray water in your home garden.

• Gray water should be used on ornamental plants and shrubs; it’s preferred to use fresh water for vegetable gardens. If you must use gray water on food plants, apply the water only to the soil, and apply to plants such as corn, tomatoes, broccoli, or other vegetables whose fruit grow above ground. Do not apply gray water to root crops such as potatoes, or leafy vegetables.
• Gray water should only be applied directly to the soil surface – an overhead or hand-held sprinkler may cause the water to splash off the soil and come into contact with the above-ground portion of the plants.
• Rotate applications of gray water and fresh water on the site.
• Apply a thick layer of mulch to areas where gray water is used to hasten the natural decomposition of waste residues.
• Use gray water only on established plants; seedlings can’t take the impurities that the waste water contains.

How Do I Transport Gray Water from the House to the Garden?

The simplest and most basic way to transport gray water from your house to your garden it to use a bucket. Keep a bucket next to the sink or bathtub, and hand carry it to the garden each time you wish to water.

A bucket can be used to transport gray water

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