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Irrigating with Greywater
By: Admin    March 29 2017 , 02:05 pm
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In order to save money and eat higher-quality food, many people are turning to growing their own vegetables. I am certainly part of that group! I look forward to this time of year but honestly, the considerable water use has always bothered me (and my bank account!).  

Like me, you are probably irrigating your yard with drinking water, since the same water that comes out of your kitchen faucet also comes out of your hose. But do your plants need drinking water? It turns out that most plants are actually perfectly happy with gently used water from showers, bathtubs, laundry and sinks: say hello to greywater!

Greywater (also “graywater") is water that has been used for washing dishes, laundering clothes, or bathing. Essentially, any water other than toilet wastes that drains from a household is considered greywater.

Greywater may contain traces of dirt, food, grease, hair, and certain household cleaning products. While greywater may look dirty, it is a safe and even beneficial source of irrigation water in a yard, and is suitable for irrigating lawns, trees, ornamentals, and food crops. Keep in mind that if greywater is released into rivers, lakes, or estuaries, its nutrients become pollutants, but to plants, they are valuable fertilizer.

Aside from the obvious benefits of saving water (and money on your water bill), reusing your greywater keeps it out of sewers and septic systems, thereby reducing the chance that it could pollute local water bodies. Reusing greywater for irrigation also reconnects urban residents and our backyard gardens to the natural water cycle. This system works well as the average American household uses about half its water indoors and the other half outside for irrigation. Some households can cut their water bills almost in half by irrigating with greywater.

The easiest way to use greywater is to pipe it directly outside and use it to water ornamental plants or fruit trees. Greywater can also be used to irrigate vegetable plants as long as it doesn’t touch edible parts of the plants. In any greywater system, it is essential to use “plant friendly” products, those without salts, boron, or chlorine bleach. The build-up of salts and boron in the soil can damage plants. Watch out for your own health as well: “natural” body products often contain substances toxic to humans.

Basic Greywater Guidelines

Greywater is different from fresh water and requires different guidelines for it to be reused:

  • Do not store greywater for more than 24 hours. If you store greywater the nutrients in it will start to break down, creating bad odors.
  • Minimize contact with greywater. Greywater potentially contains pathogens if an infected person’s feces got into the water, so your system should be designed for the water to soak into the ground and not be available for people or animals to drink.
  • Infiltrate greywater into the ground. Do not allow it to pool up or run off. Knowing how well water drains into your soil or the soil percolation rate of your soil will help with proper design. Pooling greywater can provide mosquito breeding grounds, as well as a place for human contact with greywater.
  • Keep your system as simple as possible. Avoid pumps and filters that need upkeep. Simple systems last longer, require less maintenance and energy, and money.
  • Install a 3-way valve for easy switching between the greywater system and the sewer/septic.
  • Match the amount of greywater your plants will receive with their irrigation needs.

Types of Simple Greywater Systems

From the Washing Machine:

Washing machines are typically the easiest source of greywater to reuse because greywater can be diverted without cutting into existing plumbing. Each machine has an internal pump that automatically pumps out the water – you can use that to your advantage to source the water directly to your plants.

If you are looking for a system that requires little maintenance while giving you flexibility in what plants you are able irrigate, I recommend the laundry-to-landscape system. This system was invented by Art Ludwig. This greywater system does not alter household plumbing: the washing machine drain hose is attached directly to a diverter valve that allows you to switch the flow of greywater between the sewer/septic and the greywater irrigation system. The greywater irrigation system directs water through 1? tubing with 1/2? outlets pumping water to specific plants. This system is low-cost, easy to install, and allows for flexibility in irrigation. In most situations this is the best place to start when choosing a greywater system.

From the Shower:

Showers are great sources of greywater- they usually produce a lot of relatively clean water. To have a simple, effective shower system, consider a gravity-based system (no pump). If your yard is located uphill from the house, then you will need to have a pumped system.

From the Sink:

Kitchen sinks are a source of a fair amount of water, usually very high in organic matter (food, grease, etc.). This water will clog many kinds of systems. To avoid clogging, it is recommend to use a branched drain system with mulch basins: organic matter will collect in the woodchips and decompose. Since bathroom sinks do not typically generate much water, they often combine flows with the shower water. Or, sink water can be drained to a single large plant or divided to irrigate two or three plants.

Low-tech, simple greywater systems are best suited to specific, large plants. Use them to water trees, bushes, berry patches, shrubs, and large annuals.

Catch warm-up water:

Warm-up water is all of that water that goes down the drain as you are waiting for the hot water to reach the faucet or shower, which can be quite a bit if your water heater is located far away from the point of use. To capture and use warm-up water, simply put a bucket or large bowl under the faucet when you turn on the hot water then move it out of the way when the water is hot. That water can be used to directly water house or garden plants, as it is just as clean as the rest of the tap water that gets used for those tasks.

Evaluate the ideal method of greywater reuse for your specific wants and needs. If you are considering implementing a greywater system at your home, be sure to thoroughly consider your options and perhaps consult with a greywater professional.

One final but crucial point: the rules and regulations regarding greywater reuse vary quite a bit, so depending on your location, some or all of these ways of reusing greywater may be illegal. In addition, improper management of greywater can lead to odor, pest, or pathogen issues, so it is vital to do research before putting in any sort of greywater system! 

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Jane Middleton Aug 23,2017

Great topic. Very useful information here. Thanks, GTH!

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