Backflow is a serious issue for the water supply because it can result in potentially contaminated water entering the drinking water system. It can occur if there is a drop in mains pressure or if the pressure on a property is higher than the water main pressure.
That is why all connections to the Sydney Water supply must be fitted with a backflow containment device. Most residential properties are considered to be low risk with backflow prevented by a dual check valve incorporated into the Sydney Water 20 or 25 mm meters.
Backflow Hazard Ratings
Hazard ratings are based upon the processes occurring on a site.
On a site where more than one process takes place, such as a site where water is being supplied for bricklaying, concrete mixing and cleaning site toilets, the hazard rating is based on the process with the highest risk.
Most homes are recognised as posing a low backflow risk but this changes to a higher hazard rating if either an above ground or underground rainwater tank is connected to the plumbing of the house. In these cases the plumbing and check of rating requirements needs to be entrusted to your licensed plumber – on Sydney’s Northern Beaches, JEDI Plumbing.
The construction of anything more significant than a stand alone house is rated as a high hazard by Sydney Water. On any such project the developer is required to install high hazard backflow prevention devices. This is not something your plumber has the flexibility to determine – Sydney Water will assume the rating to be ‘high’, and require the appropriate device to be installed.
To do this, accredited plumbers must then be used to install the appropriate backflow prevention. The more complex the uses of the property are and the more connections there are to different mains, the more important the hazard rating and backflow prevention installation is.
Backflow Prevention Devices
The required devices for backflow prevention vary with the hazard rating. They range from the non-testable prevention provided by 20mm or 25mm water meters to a registered break tank, and a reduced pressure zone device or registered air gap for high hazard properties.
A list of the types of devices for different hazard ratings is available through Sydney Water.
For unmetered properties a backflow containment device is required, and must comply with the hazard rating of the property.
Installing Backflow Prevention
The installation of backflow prevention devices are covered by the AS/NZS 3500.1 standards code.
Backflow prevention installation cannot therefore be a DIY project. It requires the services of a Licensed Plumber like JEDI Plumbing here on the Northern Beaches. If registered break tanks or air gaps are required then these too must be certified by a licensed plumber.
The device has to be installed on the property side of the water meter near the boundary of the property.
During installation these devices have to be commissioned and then tested by an accredited plumber. If the property is rated medium or high for backflow hazards, then a Certificate of Compliance must be submitted by the licensed plumber.
The Inspection Test and Maintenance Report has to be received by Sydney Water within two days of the completion of the work.
If the activities on a site change, a new backflow prevention device may be required. A licensed plumber is required to make a re-assessment of the hazard rating and make any necessary adjustments to upgrade the backflow prevention device.
Sydney Water may conduct a site visit to verify hazard ratings and changes to hazard ratings.
Contamination of the water supply may occur if there is a cross connection between a water supply and contaminated water source coupled with reduced pressure in the mains. For this reason plumbing work done to standard by licensed plumbers is essential, and it is why Sydney Water may instruct a hazard rating and backflow device installation on unmetered properties.
In some cases Sydney Water may restrict or cut off water supply to residential or commercial properties that do not comply with backflow prevention standards.
The JEDI Plumbing team is on hand to help the people of Sydney’s northern beaches with all of their plumbing problems – call Cameron or Debra today on 0411 774 381.