Backflow Prevention Device Installation SWMS

Backflow prevention installation covers the selection, installation, commissioning and testing of backflow prevention devices that protect the drinking water supply from contamination by preventing water flowing backwards from a property into the network. Backflow can occur through back pressure or back siphonage, and the consequences of a failure are serious: contaminated water, chemicals or other hazards drawn into the potable supply can affect the property and the wider network. The correct device must be matched to the hazard rating of the connection, and incorrect device selection is the most common compliance failure in backflow work. This document is written on the basis that backflow prevention is installed by a licensed plumber with the appropriate backflow endorsement, matched to the assessed hazard, and commissioned and tested by an accredited tester.

Backflow prevention is installed to AS/NZS 3500.1, the water services part of the plumbing and drainage standard, which classifies hazards as high, medium or low and sets the device required for each: high-hazard connections such as fire services, cooling towers and chemical dosing require a reduced pressure zone device, and medium-hazard connections require a double check valve. Devices comply with AS/NZS 2845.1 for materials, design and performance, and testable devices are field tested and maintained to AS/NZS 2845.3 by an accredited backflow tester. A single check valve is not a recognised backflow prevention device. This document coordinates the hazard-assessment, device-selection, installation and testing controls so the potable supply is protected and the installation is compliant.

Hazards identified

9 hazards covered, sorted by priority.

Control measures

Hierarchy-of-controls order: elimination → substitution → isolation → engineering → administrative → PPE.

1. 1Engineering: assess the hazard rating of the connection — high, medium or low — to AS/NZS 3500.1, and select the matching device: a reduced pressure zone device for high hazard, a double check valve for medium hazard, and the appropriate device for low hazard.
2. 2Engineering: install a backflow prevention device complying with AS/NZS 2845.1, at the correct location for containment or zone or individual protection, with the required clearances, drainage and test cocks, and never rely on a single check valve.
3. 3Administrative: commission the installed device and arrange field testing by an accredited backflow tester to AS/NZS 2845.3, with the device registered with the network utility where required and the test results recorded.
4. 4Engineering: identify and remove or protect cross-connections between the potable supply and any non-potable or hazardous system as part of the installation.
5. 5Administrative: manage the discharge and pressure release when testing a reduced pressure zone device, directing relief discharge safely and controlling water release.
6. 6Administrative: where the device is installed in a pit, meter box or confined location, apply the confined space and access controls and atmospheric testing where the location meets the confined space definition.
7. 7Administrative: manage associated water systems for Legionella and stagnation risk, flushing and commissioning the pipework so water quality is maintained.
8. 8Administrative: ensure the work is carried out and certified by an appropriately licensed plumber or gasfitter under the relevant state or territory plumbing and gasfitting licensing scheme, with a compliance certificate issued where required.
9. 9Administrative: all workers must hold a valid White Card (General Construction Induction Training, CPCCWHS1001) before entering any construction workplace, with the plumbing, gasfitting and any confined space competencies and licences required for the work.
10. 10Administrative: conduct a daily pre-start toolbox talk covering the day's work, identified hazards, isolations, required PPE and emergency procedures, and record attendance in the consultation section.
11. 11Administrative: consult workers and any health and safety representatives on the work and its risks, record the consultation, and keep this document available at the workplace.
12. 12PPE: eye protection to AS/NZS 1337.1, hearing protection where required, gloves appropriate to the task, and Class I or Class II safety footwear with protective toecap to AS/NZS 2210.3.
13. 13Administrative: review and update this SWMS whenever the work scope changes, after any incident or near miss, when a worker or health and safety representative raises a concern, when new hazards are identified, or at minimum every 12 months.

Applicable Codes of Practice

Worked example

A licensed plumber with a backflow endorsement is engaged to install backflow protection on the water connection to a commercial building that has a cooling tower and a chemical-dosed system. Because those are high-hazard connections, the hazard is assessed to AS/NZS 3500.1 and a reduced pressure zone device is selected for containment protection at the boundary, with double check valves for the medium-hazard internal zones. The devices selected comply with AS/NZS 2845.1, and each is installed at the correct location with the required clearances, drainage for the relief valve, and test cocks, with cross-connections identified and removed. A single check valve is not used anywhere as backflow protection. On completion the plumber commissions the devices and an accredited backflow tester field tests them to AS/NZS 2845.3, directing the relief discharge from the reduced pressure zone device safely during the test. The devices are registered with the network utility, the test results are recorded, and the associated pipework is flushed and commissioned so water quality is maintained. The compliance certificate is issued and the test records retained.

Related legislation

• Model Work Health and Safety Act — primary duty of care; the duty to consult workers; the reckless-conduct offence; and notifiable-incident provisions, as enacted in each jurisdiction.
• Model Work Health and Safety Regulations — Section 291 high risk construction work and the SWMS preparation and review duties, and the confined space provisions where applicable, as enacted in each jurisdiction.
• The relevant plumbing and drainage standards AS/NZS 3500 (Parts 0–5) and, for gas, AS/NZS 5601.1:2022, are called up by the state and territory plumbing and gas safety legislation.
• Plumbing and gasfitting work is licensed under each state and territory's plumbing and gasfitting licensing scheme, with compliance certification required for notifiable work.
• Victoria operates under the Occupational Health and Safety Act 2004 and the Occupational Health and Safety Regulations 2017, with the high risk construction work and confined space provisions applying in place of the model instruments.

Frequently asked questions