Cisterns and Other Rain-Catchment Systems
In many areas of the world, people get drinking water from catchment (collection) systems that trap and store rainwater. Even when these systems are constructed and used properly, they are easily contaminated by germs that can cause sickness. Some water supply systems use surfaces such as rooftops to capture and channel water to a cistern (storage tank).
When cisterns and similar systems come in contact with floodwater, you should assume that your drinking water is contaminated. If you are concerned about contamination of your drinking water source, please refer to Emergency Disinfection of Cisterns and Other Rain-Catchment Systems. Advice on cleaning storage tanks or tankers can also be found in the World Health Organization’s step-by-step guide to emergency Cleaning and Disinfecting Water Storage Tanks and Tankers [PDF - 378 kb].
If you do not get your water from a cistern or a well, refer to Personal Water Use for information on disinfecting your water.