Grey water is the domestic or household wastewater that comes from the laundry and bathroom. When treated properly this is safe for external use. Toilet water on the other hand is termed ‘black water’ and cannot be reused. Kitchen water is technically grey water; it is treated as black water as it often contains food and grease.
Water Rhapsody can help you recycle your household grey water for use on garden beds. It is an excellent way of saving water and saving money! Grey water is available every time you shower or wash with the average house creating up to 83,000 litres of grey water per year.
Your grey water is suitable for irrigating most garden areas including ornamental beds and lawns. When watering native gardens remember to use a type of detergent that has low levels or has no phosphorus.
Treatment before irrigation?
Plants and soil, especially the upper, most biologically active layer of soil, are fantastically effective for wastewater treatment. Pretreatment is often presented as an essential element in a grey water system, when in fact it may be more pointless than treating your wastewater before sending it down the sewer. Plants and soil are fine with funky, chunky water; it is pipes and people who may have a hard time with it. Pretreatment is only necessary to overcome limitations of the distribution plumbing to handle funky water. With a properly designed system, grey water can be reliably and safely distributed with no filtration whatsoever.
All grey water safety guidelines stem from these two principles:
1) Grey water must pass slowly through healthy topsoil for
natural purification to occur.
2) Design your grey water system so no contact takes place
Here are examples of applying these principles to correct possible problems:
- Direct contact or consumption. Solution: carefully avoid cross connections and label grey water plumbing, including grey water garden hoses. Use gloves when cleaning grey water filters.
- Contamination of surface water. If grey water does not percolate through the soil, it can flow into creeks or other waterways untreated. Solution: discharge grey water underground or into a mulch-filled basin. Don’t apply grey water to saturated soils. Apply grey water intermittently so that it soaks in and soil can aerate between watering. In general, contained grey water application at least 50 feet from a creek or lake is not a problem.
- Contamination of groundwater. It is all but impossible to contaminate groundwater with a grey water system. However, property owners with wells should not irrigate with grey water any closer to the well than county regulations allow for a septic tank leachfield.
- Chemical contamination. Biological purification does not usually remove industrial toxins. Toxins either will be absorbed by plants or will pollute groundwater. Many household cleaners are composed of chemicals that are unsuitable for introduction into a biological system. Solution: don’t buy products that you wouldn’t want in your grey water system. Divert water containing those you can’t avoid to poison the sewer or septic instead.
- System overload. Grey water systems are safest when using water that is fairly clean initially. Grey water should not contain water used to launder soiled diapers or by anyone with an infectious disease; in both cases, grey water should be diverted to the septic tank or sewer. Also, don’t store grey water; use it immediately, before bacteria multiply. Finally, if you are having a party where 50 people are going to use a system designed for two, consider diverting grey water to the sewer for the night.
Discharge of grey water directly into natural waters or hardscapes?
You’d think this would be more rare, because it is so obviously wrong. They come in two categories; legacy systems, from places built 50 or 100 years ago before they knew any better and/or before it mattered, and new systems, which are generally more furtive and criminal-feeling, or just so unconscious it is beyond belief.
Almost anything would be preferred. Just dumping the water on the surface of the soil is a big improvement over dumping it in natural waters or impermeable surfaces. Dumping it into a mulch-filled basin would be a vast improvement.
When the receiving body of water has sufficient capacity to purify the water, and there is no other reasonable alternative. Sailboats on the open ocean are the only example which comes to mind. Even if you are in the middle of a vast wilderness next to a large river, you can just take a few steps back and rinse the shampoo onto soil, which will purify it before it goes into the river.
Irrigation of plants which can’t take it
Certain plants cannot take grey water, and certain plants can’t take too much of any kind of water. Acid-loving plants tend to have a hard time with grey water, and certain plants which are native to dry areas have a hard time handling any irrigation in the dry season. Also, some cultivated plants have problems with soggy conditions.
This problem is not a commonly encountered one.
Avoid irrigating plants which don’t want the water, and design your system so it doesn’t create soggy conditions for plants that can’t handle it.