Grey water is the wastewater resulting from household usage, such as washing dishes and clothes and bathing. (The term grey water is used for this type of wastewater as opposed to that containing sewage and biohazards, which is termed “black water”.) Other sources of grey water might include air conditioning drip (which can be gallons per day depending on usage!), and roof condensation.
The amount of water we use to shower and clean is huge compared to that which we actually consume. In light of what some say are inevitable water shortages to come, some home and building owners have started recycling or reusing grey water for their gardens, or to flush toilets with. So, is it always worthwhile to reuse grey water? And how do we go about it?
Unfortunately, we have to consider the safety of grey water--is it really OK to untreated or soapy water in our gardens, for example? In some places, there are stringent regulations on grey water use, and it can be more expensive to recycle it, making it tough for many homeowners to justify. However, it’s important to know that as long as grey water from a home is collected separately from the black water, the system can use filtration and/or microbial treatments to make it clean enough for irrigation. Some types of filtration include sand filtration or biological systems, such as filtration ponds. In order to find out more, ask your landscaper about it, as they’ll also have the best interests of your plants in mind, and they can advise you on the best solution for grey water irrigation.
What are some things you can do now?
If you have an external air conditioning unit, collect the drip water from it using a hose and container, and use it to water your house plants and/or garden. In warm, moist climates this can literally be tens of gallons per day from one household.
Collect dew drip from all your downspouts (similar to rain water harvesting, which I’ll talk about next week).
There are relatively simple systems for collecting bathroom sink water to flush the toilet, which you can install yourself or get a plumber to do. There are even toilets with built-in sinks right in the top!
For more about indoor reuse of grey water, look up the International Plumbing Code, which, as opposed to the Uniform Plumbing Code, enables reuse of grey water in the home.