WATER SERVICES

Backflow prevention and cross-connection control, explained

Backflow prevention is about one thing: stopping water that could be contaminated from flowing back into the drinking supply. The hazard level decides the device, and the testable devices need records.

What a cross-connection is

A cross-connection is any point where non-potable water, or water that could become contaminated, can connect to the potable supply. Under the right pressure conditions, water can flow the wrong way and carry that contamination back into the drinking system. Backflow prevention is what stops it.

Hazard ratings and devices

The control required scales with the hazard. Lower-hazard situations may be handled by an air gap or a dual check valve; higher-hazard situations call for a registered, testable device such as a reduced pressure zone (RPZ) valve installed upstream. Matching the device to the hazard rating is the core of getting it right.

The records that matter

• The device type and where it was installed.
• For testable devices, the commissioning and test records.
• Photographs of the device in place and its markings.

Common questions

What decides which backflow device I need?

The hazard rating. Lower-hazard situations may use an air gap or a dual check valve; higher-hazard ones require a registered testable device such as an RPZ installed upstream.

Do testable backflow devices need records?

Yes. Testable devices generate ongoing commissioning and test records, which are best captured against the job rather than on a loose form.

General information for licensed tradespeople, not legal or regulatory advice. The licensed plumber remains solely responsible for compliance. Refer to the current AS/NZS 3500 standards and the Building and Plumbing Commission (formerly the VBA) for authoritative requirements.