Back flow


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Terms & Synonyms

Official WHO Definition

Back flow is the unintended reverse flow of water or other substances into distribution pipes of drinking water from an unintended source which is capable of polluting the drinking water (American Society of Sanitary Engineering 2007). The reversing of the normal flow of water or other substances into the drinking-water distribution system from any unintended source (WHO 2006).

Other Definitions


Interpretations and Explanations

Back flow in a drinking water supply happens when pressure is reduced such that flow can occur in the direction opposite to the intended flow. This can result in flow of contaminated water into drinking water plumbing if there is a connection with contaminated water that allows that flow to occur. Plumbing codes demand that the integrity of a drinking water supply be protected at all times. The level of protection required is based on the potential level of risk. All plumbing codes for water supply systems specify the need for backflow protection (World Plumbing Council Working Group 2008).Drainage systems should be designed and constructed so that sewage cannot enter buildings connected to the sewerage system in the event of backflow from the public sewers due to flood, blockage or any other cause (WHO 2006).


 American Society of Sanitary Engineering (2007) Plumbing Dictionary, 6th ed.WHO (2006) Health aspects of plumbing

WHO Lexicon page (translations and examples)

See also

External Resources


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