Urban
Water
Definition of Backflow
Backflow is a term commonly used in the water industry to describe
a situation where an unintended flow of water passes from a customer's
property back into the Authorities water mains.
A common Backflow occurrence may be, for example, an industrial
site where a hose is left submerged in a vat of hazardous chemical
liquid .The Water Authority attend a broken water main further down
the street. To repair the water main the Authority need to dig down,
cut out a section of the main and replace it with a new section
of pipe. The opportunity for Backflow to occur is at this stage
is when the section of damaged water main is removed. The remaining
water in the main drains out creating a type of siphon affect on
properties upstream .The vat of hazardous liquid containing the
garden hose is completely sucked dry, the hazardous liquid ending
up in the Authorities water main.
Reported occurrences of Backflow are rare, but the potential for
an isolated incident similar to the above to occur pose a significant
risk to the Authorities infrastructure and customers.
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Backflow
Prevention
The most common form of prevention against
Backflow is via the installation of an extremely sophisticated valve
(Backflow Prevention Device). In 1997 Lower Murray Water introduced
a Backflow Prevention Policy. The owners of properties where a potential
risk was identified were contacted and advised that there would
be a requirement for them to have one of these devices installed
on there water connection.
In most instances the device is installed immediately upstream of
the water meter. (This is referred to as containment protection).
There are currently around 300 Backflow prevention Devices installed
across the Authorities region. These devices are normally located
on non-residential properties .The Victorian Plumbing Regulations
also requires that a registered person carry out an annual maintenance
check of these devices, the results of which are passed on to the
Authority. For all other properties the Authority address the Backflow
potential via the installation of a new type of sophisticated water
meter known as a Dual Check Valve meter. An ongoing water meter
replacement program will ensure that all properties are adequately
protected from Backflow. |
