I must say a word about rainwater harvesting and rain barrels in general. Rainwater harvesting and rain barrels in general are very good ideas. The un-purified water from a rain barrel is still quite useful for all kinds of things – such as washing a car, irrigating lawns, flowers, shrubs and any non-edible vegetation around your house. Most importantly, rain barrels retain runoff from roof surfaces and help to limit excessive surface water runoff from residential areas, and provide water for irrigation of decorative plants without using potable water. This is extremely important to the health of the environment, and water conservation. So, please do not let this site discourage you from setting up rain barrels. A fine screen on top of a 55 gallon barrel, along with clean gutters, is really all that is needed to provide the simplest form of “filtration” for rain water harvesting from a rooftop. Just remember that the water is usable only for non-potable purposes where the water will not be consumed directly or indirectly.
The filters described here on this blog, and on the websites:
are meant to produce pure water beyond what is contained in a rain barrel. A slow sand filter, and a first flow diverter are added extras for those who are really into the science and process of water purification – perhaps the next step for those who are already familiar with setting up and using a rain barrel to capture roof water.