Things to note that were not mentioned in this article:
There are restrictions on what states can collect rain water. Be sure to check and see if this is legal in your state first.
The levels of pollution, pollen, mold, and other contaminants are low — possibly lower than your public drinking water supply. Keep in mind, rain does pick up low levels of bacteria as well as dust and occasional insect parts. If you're collecting rainwater from the roof, there are even more contaminations and chemicals that are introduced by the roofing material, as well as any bacteria and trash that may collect on top of your house. Therefore, cleaning your car, windows, it watering your plants may not be such a good idea.