by Amber

Should You Recycle Greywater for Plants?

Even if you’re not in an area suffering from deep or prolonged drought, it makes a lot of sense to recycle greywater for plants. Why throw it away if it’s not toxic or potentially harmful? Especially when you pay for it by the gallon from the city water system. After all, while you wouldn’t want to drink it, or bathe in it, plants in the yard can benefit from the water. So, why pay the city to recycle it and sell it to you again? You get multiple uses per gallon, can water the garden during water rationing, and grow food for far less.

This recycle greywater thing isn’t just for arid climates, city residents, and suburbanites. Your water at a rural home may come from a private well, but you’re paying for the electricity to pull it out of the ground. And wells do go dry. Then there’s the wear and tear on your septic system. While your septic tank needs some water to function properly, running less greywater into it means less frequent clean-outs too.

A simple system to recycle greywater for plants isn’t super expensive or complicated. Depending on gravity means no need for expensive pumps to move water from your washing machine to important plants in the yard. The cost is only $200 or less, if you do the work yourself. How you intend to use it will have a great deal of influence on the total cost to install it too. There’s an excellent guideline of the system needed for different yard and garden applications  on the Clean Water Components website. As you can imagine, the cleaner you need to make the greywater, the cost of the recycling system increases right along with its complexity.

It might sound like a great idea to reclaim water from the bathtub or shower for landscaping irrigation. But personal care products in use may make this bad for your plants, and your soil. One might think that all the water passing through the kitchen sink is pretty safe for reuse too, but it’s not. Raw and non-composted food particles can introduce pathogens to your soil. The safest greywater to reclaim for the yard comes out of your washing machine. This is the easiest source to control the level of plant and soil harming possibilities. And surprisingly, there are numerous reasons why diverting greywater to irrigation isn’t advisable.

You can only recycle greywater for plants if all the detergents, shampoos, body soaps, and so on that is mixed with the water is made with a plant-friendly formula. Earth-friendly only means it won’t harm the environment. Many such products contain things like salts, peroxide, boron, anti-bacterials, and more that are harmful to plants. So, you’ll only want certain kinds of greywater being taken up by the plants living in your yard. Salts kill many kinds of plants, as does borax or boron. The Ecology Center has a detailed article on what you don’t want included in greywater used in the landscape.

If you have a water softener, you wouldn’t be able to recycle greywater. The unhardening process involves salt. Outdoor faucets never draw water that passes through a softener. Not to save the homeowner money on monthly maintenance, but because the salt is harmful to most lawn grasses, ornamental and garden plants, shrubs, and trees.

The simplest greywater recycling system doesn’t have an actual filter. Instead, the water is pushed through soil and mulch to remove the chunkiest impurities like lint and fibers. That’s not fine enough filtering for running through an irrigation system, and it doesn’t remove whatever is in the soaps the water contains. That being said, not all plants will be happy with unfiltered greywater irrigation.

Even if you do use only plant-friendly detergents and personal products, it’s best to only water large woody plants with greywater. That would be your  trees, woody shrubs, and large perennials. Unless, of course, you want to invest a lot more into a greywater system – more money, complexity, and maintenance. Without a sand filter and a drip irrigation system, you can use it only on large plants, which doesn’t include most edible crops. Clean Water Components advises to keep the system as simple as possible. They also warn you to never allow greywater to come in contact with edible portions of plants. Since you eat the root of crops like carrots, potatoes, and radishes… don’t use greywater near them at all. Also, you can only use greywater for subsurface irrigation. Totally ruling out overhead sprinklers, hand-held hose sprayers, and watering cans.

Furthermore, if you’ve got a high water table – or live within 100 feet of a river, stream, or lake – you can’t recycle greywater for plants in your yard. In both cases, the greywater will readily mix with natural waterways. You don’t want greywater in soils where ground water levels are 3 feet or less below the recycled water drainage.

Unlike rainwater, you can’t store greywater. It has to pass from the surge tank into the drainage system right away. The tank is only there to prevent flooding and reduce the force of washing machine ejection. The small diameter pipes it drains out to your engineered deposit spots can only move so much per minute. Bigger pipes would handle a lot more gpm, but they’d also cost more and require a lot more labor to install.

In some places, installing any greywater system requires a permit. In others, no permission is needed to put in a recycle greywater from the washing machine to water outdoor plants. But there are also states that do not allow greywater irrigation systems at all, so check the codes and regulations where you live. The safest way to recycle greywater anywhere is using it for flushing the toilet. Then you don’t have to worry so much about what is in it that could damage your plants or the environment, or plug irrigation tubes or emitters

More Info/Sources:

Featured image courtesy of Day 1 Solar.

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The garden played a starring role from spring through fall in the house Amber was raised in. She has decades of experience growing plants from seeds and cuttings in the plot and pots.