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).

Floods and heavy rains can wash large amounts of debris and pollutants into cisterns and rain catchments systems, causing drinking water contamination. 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 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 – 4 pages].

If you do not get your water from a cistern or a well, refer to Emergency Water Supply Preparation for information on disinfecting your water.

IMPORTANT: Water contaminated with fuel or toxic chemicals will not be made safe by disinfection. Do not enter the cistern. Gases and vapors can build up, creating a hazardous environment.