Backflow Reference

Common backflow scenarios and preventer types.

Reference

Hose bibb to grade or yard Atmospheric vacuum breaker (AVB) or hose-bibb vacuum breaker.
Lawn irrigation, no chemicals Pressure vacuum breaker (PVB).
Lawn irrigation with chemicals or boilers Reduced-pressure principle assembly (RPZ).
Fire sprinkler systems Double-check valve assembly (DCVA) or RPZ depending on hazard.
Commercial dishwasher Air gap or RPZ depending on chemical use.
Boiler with chemical treatment RPZ.

Details, formula, and sources

(reference page; no compute) Common backflow hazards mapped to typical preventer types (RP, DCV, PVB, AVB, AG) per the cross-connection categories described in IPC 2021 Section 608 / AWWA M14.

IPC 2021 (International Plumbing Code). Section 608. AWWA M14 by name.

Free read-only access at codes.iccsafe.org. AWWA M14 licensed; cross-connection program guides free at most state primacy agency sites.

Estimate. AHJ and licensed plumber / gas fitter govern. Verify against the IPC / IFGC edition adopted in your jurisdiction.