Grey Water Reuse vs. Rainwater Harvesting

creative commons photograph by Weighn

The EPA tells us that less than 1% of the water on earth can be used by people. “Of the 26 billion gallons of water consumed daily in the United States… 30 percent is devoted to outside uses. The majority of this is used for irrigation.“ Colorado is very dry, which makes water conservation a very important topic.

Maybe you have heard of "grey water collection" or "rainwater harvesting”? The Colorado Extension office has some very detailed explanations of both of these topics. This article is a condensed presentation on the differences between the two, sourced from the extension office.  A follow up article will provide links to some projects you can do yourself to catch your water, save it, treat it, use less of it, and reuse it!

First off, what is the difference between Grey water reuse and Rainwater Harvesting?

Let’s start with some definitions:

Tap Water: highest quality water. Tap water is processed to be clean enough to drink!

Grey water: middle quality, this is water drained from baths, showers, washing machines and bathroom sinks.

Black water: lowest quality, this is water drained from the kitchen sink, garbage disposal, dishwasher, and toilet.

High concentrations of organic waste in blackwater make reusing that water very difficult. However, grey water can be great for reuse in irrigation or other applications. This is known as grey water reuse.

Because grey water may contain bacteria, it is best to filter and use on non-edible landscape plants. Even so, in the state of Colorado, permits may need to be attained to set up and reuse your grey water. Please consult the extension office fact sheet for more information, which can be found through this link: http://www.ext.colostate.edu/pubs/natres/06702.html.

Whether you are trying to save money, concerned about water conservation, or trying to live off of the grid, rainwater harvesting will likely come up in your research. Rainwater harvesting is just what it sounds like: the collection and reuse of your rainwater! Rainwater can be capture in vessels that are simple to construct from inexpensive local materials.

Though rainwater is relatively easy to collect, most rainwater is not potable; it may contain unrecommended “ingredients” such as bird feces or mercury from coal burning buildings. In order to best avoid contamination, filter and screen out impurities before they enter the storage container. The good news is that our extension office in Colorado reports that the rainwater quality here is generally good! Though it may not be suitable for human consumption, it’s usually fine to use for flushing toilets, washing clothes, watering the garden, washing cars, and livestock watering.

Now that you understand what exactly grey water reuse, and rainwater harvesting are, do a little rain dance and keep your eyes peeled for more information on how to do-it-yourself!

written by Roxanna Shohadaee