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Roof-catchment cisterns may also be used to supply water to farms. Watering troughs and rain barrels can be filled by water collected from barn and other out-building roofs. A storage cistern built alongside a barn or other building could serve as an emergency source of water for firefighting in the event that a pond were not nearby. However, the use of rainwater for supplying domestic water needs is not without its problems.

Water quality is of concern especially when the rainwater is to be used for drinking purposes in addition to other domestic uses. Rainwater and atmospheric dust that are collected by roof catchments contain certain contaminants which may pose a health threat to those consuming the water. Lead and other pollutants may accumulate in cistern bottom sediments; and untreated rainwater is quite corrosive to plumbing systems. Measures must be taken to minimize these and other water-quality problems in cistern systems. Recommendations for doing this will be presented, as well as guidelines for designing and building roof-catchment cistern systems.

Rainwater cisterns can provide water of adequate quantity and quality if proper steps are taken in the planning and construction stages, and periodic maintenance is performed throughout the life of the cistern.