<Table> <Tr> <Td> </Td> <Td> This article does not cite any sources . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (April 2014) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article does not cite any sources . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (April 2014) (Learn how and when to remove this template message) </Td> </Tr> <P> A vacuum breaker is an attachment commonly placed on a bibcock valve or toilet or urinal flush valve, that prevents water from being siphoned backward into the public drinking water system . This prevents contamination should the public drinking water system's pressure drop . </P> <P> A vacuum breaker typically contains a plastic disc that is pressed forward by water supply pressure, and covers small vent holes . Should the supply pressure drop, the disc springs back opening the vent holes (which let in outside air), and preventing backflow of water . </P>

What is the function of a vacuum breaker
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