Backflow prevention
Backflow prevention stops contaminated water from flowing back into the potable supply. Required under AS/NZS 3500.1 on residential builds.
Ask Chalkline about this →Backflow prevention is the use of mechanical devices or design techniques to stop water from flowing backwards from a potentially contaminated source into the drinking water supply. On a residential build, AS/NZS 3500.1 requires backflow prevention devices at connections rated according to hazard class: low-hazard connections (most domestic fixtures) may use check valves or air gaps, while high-hazard connections (irrigation systems, pool fill valves, certain appliances) require testable devices such as reduced-pressure zone (RPZ) valves. The 2025 edition of AS/NZS 3500.1 elevated atmospheric vacuum breakers to high-hazard testable devices and introduced new provisions for flexible hose connections. Backflow prevention devices must be accessible for testing and maintenance.
Also known as: backflow preventer, backflow protection
Category: Plumbing compliance
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Last updated: 2026-05-08. Verified: 2026-05-08.