A hose in a bucket, and the backflow it can carry

What backflow is, in three authorities’ words

Backflow is a reversal of the normal direction of water flow in a water supply plumbing system, and it happens when the water delivery main is at a lower pressure than the internal plumbing system, a condition called back siphonage. A property’s drinking water supply can also be cross connected deliberately, by a bore pump pushing bore water at a higher pressure than the mains, or casually, by a hose left submerged in a container of liquid. Central Coast Council defines a cross connection as any connection between drinking water and another water source that is not safe for consumption, such as recycled water, wastewater or stored water.

The consequence is what makes the fitting matter. NT’s Power and Water Corporation puts it as plainly as any page in this guide: used water that may be contaminated goes back into the drinking water and could end up in someone’s glass, and a severe backflow incident may endanger a person’s health, or in extreme cases their life. A backflow prevention device acts as a barrier, allowing water to flow in one direction only, from the water main into a property; if water begins to flow the wrong way, the device shuts or diverts the flow.

When a home needs a device, and when another body has provided it

This is the part the authorities answer differently, and the difference turns on the size of the connection and the risk of what is on the property. Central Coast Council says a backflow prevention device is not required for 20 mm and 25 mm water service connections providing drinking water to a single, low hazard residential dwelling, and that an accredited backflow plumber must be engaged to assess the site’s hazard rating. Water Corporation in WA reaches the same end from the meter’s side: new meters 20 mm and 25 mm in size come with integral dual check valves, so low risk properties such as residential only, with only metered services of this size, already have sufficient backflow prevention.

Where the risk is higher, the device is not optional. WA classes backflow risk as low, medium or high: medium risk is any condition, device or practice that could endanger health, and high risk any that could cause death. The property’s initial rating is given at approval, and site-specific activity determines the final level, with certain commercial and industrial processes defaulting a property to high. Central Coast Council requires a device for properties identified by a plumber as having a medium to high hazard of backflow contamination of the drinking water system.

Sydney Water goes further and makes the device universal on paper: all drinking and recycled water connections must have backflow containment protection to reduce the hazard a property might pose to the water supply, and property owners are responsible for ensuring their connected property has the correct device on its water service. Owners of commercial or industrial properties, and any other property with an on-site process, must get an accredited backflow plumber to assess the cross-connection hazard rating, or Sydney Water will classify the property as high hazard.

Whichever rule applies, the device is not a householder’s fitting. WA says only a licensed plumbing contractor may install backflow prevention devices. Victoria defines backflow prevention work as the repair, alteration, maintenance, testing or commissioning of a testable device listed in the Australian Standard, and its plumber classes page lists the unit on commissioning and maintaining backflow prevention devices among the requirements to become registered or licensed in that class.

The yearly clock, authority by authority

Once a testable device is in, it is tested on a clock and registered with a body, and each authority sets its own periods.

• WA: testable devices at the property boundary, those on medium or high risk properties and fire services, require testing at commissioning, after any maintenance, and every 12 months by an accredited tester; registration is to be submitted no later than 5 working days after the test, and maintenance is only to be done by a licensed plumbing contractor. A test report goes in online no later than 5 working days after the test.
• Queensland: the owner of premises must register the testable device with the local government in the approved form, and arrange for a backflow prevention licensee to maintain and test it at least once each year after it is registered. The Act also makes it an offence to remove a device or to do anything that makes it inoperable.
• The ACT: an owner with one or more devices must have them registered with Access Canberra at the time of installation and tested by a licensed plumber every 12 months. Only a licensed plumber endorsed to test devices can complete the report, and the plumber submits it to Access Canberra; the initial test is free and registering an annual test is $26.00 per report.
• Central Coast, NSW: testing of all testable devices must be conducted annually, with results submitted to the council each year, and there is no fee for the annual inspection and maintenance report. The council maintains a register of testable devices and monitors compliance; where a device does not comply it may issue a notice requiring repair, maintenance, testing or replacement.
• Sydney Water’s area: if the annual inspections at a property are not completed, Sydney Water may organise a plumber and charge the owner for the service.
• The NT: an owner of a business or multi-dwelling may be required to have a device and to have it tested every year; a backflow accredited plumber assesses the hazard level, and medium and high risk properties must have a testable device installed.

The garden tap, and the hose

The garden tap is where a householder’s own work runs closest to this. Queensland’s unregulated list includes installing or maintaining an irrigation or lawn watering system downstream from a tap, isolating valve or backflow prevention device on the supply pipe for the watering system, so that side of the device is a householder’s. The device and the supply side of it are the plumber’s, and the reason is the hose’s own habit: the example WA gives for a cross connection is a hose submerged in a container of liquid, and the pollution it carries can enter the water supply when the pressure drops.

The hose is not the only quiet cross connection. The ACT’s list of where devices are typically installed runs from large commercial buildings such as offices, apartment complexes, universities, schools and hospitals to anywhere there is a medium to high risk of backflow occurring, such as an irrigation system or a rainwater tank connected to the main water supply.

Where practitioners cannot achieve the required height for an overflow relief gully, NSW allows a reflux valve as a substitute, with a condition attached about what is not installed upstream of it. And the community’s side of the bargain is stated by WA: the community has a right to protection from contaminated water as a result of a backflow incident.

One device, one year, worked through

Take a house whose assessment comes back medium risk, in a state that follows WA’s pattern. The device goes in on the owner’s side of the water connection at the boundary, and devices should not be buried in the ground. It is tested at commissioning; when maintenance is done it is tested again; and it is tested every 12 months after that. Each test is followed within 5 working days by a report, the registration going to the water authority and the test report going in online. If the device fails or is not maintained, the authority’s remedy is a notice to the owner or occupier, and in WA a non-compliance notice follows a failure to maintain a device.

A property may also appeal a rating: WA allows an owner who considers the assigned risk rating higher than the site’s activities warrant to appeal within 28 days of being advised of the rating, with the outcome advised to the property owner. Water Corporation’s backflow pages are where that state sets it all out.