Back siphonage

Slovak term: Slovenský termín

1. Back siphonage is the reverse flow of water within a water supply system due to negative pressures in the pipe system enabling atmospheric pressure to force the flow of water backwards through a siphon action (World Plumbing Council Working Group 2008).
2. The reversing of normal flow resulting from negative or subatmospheric pressures in the distribution piping of a drinking-water supply system (WHO 2006).

Explanation

Back siphonage can occur as a result of excess demand such as fighting a fire where unusually large volumes are required and pressure is reduced (World Plumbing Council Working Group 2008).

Example

Back Siphonage can be found if a water system is turned off, thus reducing the pressures to below atmosperic pressure and enabling the a negative or vacuum pressure to be formed drawing contaminated substances into the water system.

The draw down or emptying of a hot water unvented pressure storage container will create vacuum, thus back siphonage will take place if a vacuum breaker valve is not installed (World Plumbing Council Working Group 2008)

References

• WHO (2006) Health aspects of plumbing
• World Plumbing Council Working Group (2008)

Links

• WHO — The Health and Environment Lexicon