Back water valve


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Terms & Synonyms

Official WHO Definition

Back water valve, sometimes referred to as a reflux valve or surcharge protection device, is a device used in drainage systems which only permits the drain to flow in one direction. It has a check valve arrangement which closes against any reverse flow. (American Society of Sanitary Engineering 2007). A device for preventing sewage or drainage water from flowing back into a building in the event of flooding or sewer blockage (WHO 2006).

Other Definitions


Interpretations and Explanations

A back water valve, sometimes referred to as a reflux valve, surcharge protection device or a blackflow prevention device, is designed to prevent any reverse flows of sewage, usually from a public sewer network operator’s asset into a private property. The reverse flow of sewage can be caused by a number of factors including; sewage backpressure due to blockages, or from storm water overloading, or from a sewer system which is undersized. The highest risk is usually at the lowest elevation in a sewer network. Properties at the foot of hills are more vulnerable than those at the top. In high risk or flood prone areas, plumbing codes may make the installation of a back water valve a mandatory requirement (World Plumbing Council Working Group 2008).


American Society of Sanitary Engineering (2007) Plumbing Dictionary. Sixth Edition Standards Australia/Standards New Zealand (2003) Plumbing and drainage. Part 0: Glossary of terms. AS/NZS 3500.0:2003  WHO (2006) Health aspects of plumbing

WHO Lexicon page (translations and examples)

See also

External Resources


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