Backflow Prevention, Cross-Connection Control, and Potable Water Protection
Backflow Prevention, Cross-Connection Control, and Potable Water Protection. This domain tests how potable water is protected from contamination. Expect questions on backpressure, backsiphonage, air gaps, testable assemblies, vacuum breakers, and the hazard-level rules that choose the correct device.
Core rules
- A cross-connection is any actual or potential connection between potable water and a contamination source. Backflow occurs by backpressure or backsiphonage.
- An air gap is the best protection because it provides a physical separation. Testable assemblies include reduced-pressure zone (RPZ) assemblies and double-check valve assemblies (DCVA).
- Selection follows hazard: RPZ for high health hazards and backpressure; DCVA for lower hazards without backpressure; pressure vacuum breakers and atmospheric vacuum breakers only where code allows.
- Testable assemblies must be tested by an approved tester at installation and at required intervals. They must be accessible and protected from freezing.
Worked example
An irrigation system has a fertilizer injection point. Because chemicals can be drawn into the water supply and the system may be under backpressure, an RPZ assembly is the appropriate choice, not a simple atmospheric vacuum breaker. The reasoning: the hazard is high and backpressure is possible. The RPZ provides testable protection against both backsiphonage and backpressure.
Common traps
Do not use an atmospheric vacuum breaker under continuous pressure or where backpressure can occur. Do not bury a testable assembly in an inaccessible vault. Do not assume a hose-bibb vacuum breaker protects a chemical injection system. Do not skip annual testing.