In its simplest form, Back flow occurs when water flows in the opposite direction to what it is expected to flow. The water is intended to flow in one direction and for a reason it flows in a different direction.

A sudden and unexpected drop in water pressure normally causes backflow. Some of the causes for this can be water main bursts, pipes freeze or unexpectedly high demand on water system. This automatically creates a negative pressure in the water supply system.  When a backflow occurs, reduced pressure may allow contaminated water from the ground, storage or other sources to enter the system.  One of the biggest concerns is that this allows drinking water to be contaminated via a cross-connection.

A properly installed and maintained backflow device will ensure water flows safely by automatically trapping water that begins to flow in the wrong direction.  This prevents water from a property being drawn back into the main drinking water supply and causing cross-connection.

The risk ratings of a home or building will determine what type of backflow device will need to be installed.  Homes and buildings are classed as low, medium or high risk.  A professional plumber from Melbourne 24 Hour Plumbing or Mr. Plumber Sydney who are accredited plumber can confirm the risk rating of your property.

A typical backflow assembly unit will have test cocks and shut off valves.  Backflow devices must be thoroughly tested when they are installed, relocated or repaired.  Backflow devices must also be tested annually to ensure they are in proper working order.

Sydney Water States the following about backflow:

Each backflow prevention containment device must be tested on an annual basis.  This is a condition of connection to the water supply.  It means that the device is maintained and continues to operate effectively.  The annual test will ensure the drinking water supply is protected from backflow.

If a device is defective or faulty, it may:

• not prevent a contaminated source entering the drinking the water supply
• cause water to be wasted through leaking devices
• impact on the water pressure supplying your property

A backflow prevention accredited licensed plumber will need to test all of your devices.  After testing your devices your licensed plumber will submit his report within 2 days on the Sydney water website stating if the device is installed correctly and if it has passed or failed the test.  The plumber will give you a copy of the Backflow Prevention Device Inspection and Maintenance Report.  If a valve fails the test and is not repaired or replaced Sydney water can disconnect you from the main water supply.