Health, Safety, Backflow Prevention, and Water Conditioning
Health, Safety, Backflow Prevention, and Water Conditioning
This domain tests cross-connection control, backflow prevention devices, water treatment, and health-related installation practices. The exam expects you to select the correct backflow method for the hazard and to know when testing and annual inspection are required.
Core rules
- An air gap is the strongest protection. A reduced-pressure zone (RPZ) protects against high hazard and backpressure; a double check valve assembly (DCVA) protects against low hazard and backpressure; a pressure vacuum breaker (PVB) protects against backsiphonage; an atmospheric vacuum breaker (AVB) cannot be under continuous pressure.
- Testable assemblies require installation by qualified personnel, annual testing, and records. Do not install a PVB below grade or where it can be submerged.
- Water conditioning includes softening, filtration, and disinfection. Install treatment equipment with bypass, backflow protection, and drain connections sized for backwash.
- Thermal expansion control is required when a backflow preventer creates a closed system.
Worked example
An irrigation system has a chemical-injection fertigation unit. Because a chemical can be drawn into the potable supply, this is a high-hazard application. Use an RPZ, not an AVB or a simple check valve. Install it above grade, provide drains, test it at installation and annually, and keep the injection point downstream of the RPZ.
Traps
Do not use an AVB where it is under continuous pressure. Do not bury a PVB. Do not rely on a single check valve for a high hazard. Do not forget expansion control after installing a backflow preventer.