The Texas Guide to Rainwater Harvesting suggests the addition of one liquid ounce of chlorine bleach per 100 gallons, or one and a quarter cup per 1,000 gallons. This method is often accompanied with an active charcoal filter, which is used to remove the chlorine before it leaves the tap. Iodine can also be used, like chlorine, to kill microbiological organisms in rainwater. Iodine tablets can be purchased at local drug and camping goods stores. Similar to chlorine, iodine treatment should be accompanied with an active charcoal filter, in order to remove the iodine before it leaves the tap.
Boiling water is another disinfection treatment and the most common with small-scale use.
Any heat source, from a campfire to a microwave, can be used. Therefore, the boiling of rainwater takes place outside of the rainwater catchment system and might require a separate holding tank. Drawings and Text by Amy Stout, March 2000 Resources Buehrer, Mark. EPA Office of Ground and Drinking Water. Emergency Disinfection of Drinking Water.