Steve Gale, Facebook asked:
Is it safe to use grey water, water from the sink or from the shower et cetera, to water things like fruit trees or crops in your garden?
David - Yes. I think I would be perfectly happy to water my flowerbeds with gray water but I think I would be just a little bit cautious about watering fruit or vegetables that you were going to eat, just as a precautionary measure.
Ben - So what sorts of problems could you actually build up in there? Is it going to fill up with pathogenic bacteria or is it purely just a case of, ďWe know itís been used, we know itís got the chemicals in it from say, your shampoo, and they may impact on the soil quality".
David - Itís both of those. I mean, there's the shampoo chemicals that might be taken up by the plant and certainly, even though this grey water comes from maybe the sink, it can also come from the shower and the bath. That can also have pathogenic bacteria in it.
Ben - He also mentions another one which is the runoff the drip collected from an air-conditioning unit. Now air-conditioning, essentially the water that comes out, is distilled water. Is that likely to be a problem? Presumably, itís going to be pure and clean, and really healthy water, but is it an issue to be putting distilled water on our plants?
David - No, I don't think that's an issue but I would just be slightly cautious with air-conditioning units of any type because of the issue of legionella which can cause Legionnairesí disease in very extreme circumstances. Now I'm not suggesting it would cause a problem in this case, but I would be cautious with that water.
Keep in mind that there is a difference between personal home systems, and public systems.
It may not be simply a case of damaging your soil. There are a great many chemicals used in many household cleaning products and personal hygiene products. There are also those home hair colouring products, some of which contain peroxides.
You bring up some very good points, Don_1, and it makes me wonder why we would use these products on our bodies and "clean" our homes with them if they are toxic. It makes sense to me to use only products that would be safe for a grey water system. Donnah, Fri, 9th Mar 2012
I work as a salesman for a company that manufactures an electronic capacitor based water treatment system that is used in cooling towers, chillers, evaporative coolers and heat exchangers to control scale, bio fouling and corrosion. By keeping bacteria levels extremely low there is no slime in the system for the growth of legionella, as legionella does not manufacture the slime but needs it to grow. We can eliminate the use of chemicals within the above systems which would traditionally be used to control scale, bio fouling etc. That being said, we are able to reuse the non-chemically treated discharge water for irrigation. Can this discharge water be safely used for food crops? Will this have a negative effect on my septic tank and the bacteria if this is connected to the water line coming into the house? It has been shown our product will reduce water surface tension by 20 to 25%, allowing for better saturation into the soil, better nutrient uptake by the roots and allowing the salts to permeate into the soil away from the root zone, all allowing for documented higher crop yields. I have been told the unit will keep the nutrients from settling out of solution for a period of up to 2 weeks in city water, 2 to 4 weeks in well water. Will this allow for a longer time between changes of nutrient solution in my hydroponics system reservoir, due to a longer period of time of nutrients staying in dispersion? greenman, Tue, 20th Mar 2012