CSLB C-36 Plumbing ContractorPlanning and EstimatingHard
A plumbing contractor is reviewing the project specifications for a new commercial building that will incorporate a rainwater harvesting system for non-potable uses, such as irrigation and toilet flushing. The plans specify the use of a cross-connection control device to prevent contamination of the potable water supply. Which type of device is typically required for severe hazard cross-connections in such systems?
- AA reduced pressure principle backflow preventer (RPZ)
- BA spill-resistant vacuum breaker (SVB)
- CA pressure vacuum breaker (PVB)
- DA double check valve assembly (DCVA)
Show answer & explanationAnswer & explanation
Correct answer: A. A reduced pressure principle backflow preventer (RPZ)
Rainwater harvesting systems for non-potable uses are typically classified as severe hazard cross-connections due to the potential for untreated water to contaminate the potable supply. A reduced pressure principle backflow preventer (RPZ) is the most robust and commonly required device for severe hazard protection.
Why the other options are wrong
- B. An SVB is similar to a PVB but designed for continuous pressure, however, RPZ offers superior severe hazard protection.
- C. A PVB is used for moderate to severe hazards, primarily for irrigation, but requires air gaps and cannot be under continuous pressure, making RPZ more suitable for direct connection to non-potable systems.
- D. A DCVA is suitable for low to moderate hazard cross-connections, not severe hazards like non-potable rainwater.
Cross-Connection Control (Severe Hazard)
The use of specific backflow prevention devices to protect the potable water supply from contamination by non-potable sources that pose a severe health risk if cross-connected.
- Severe hazard situations involve substances that could cause death or illness.
- Rainwater harvesting for non-potable uses is typically a severe hazard.
- Reduced Pressure Principle Backflow Preventers (RPZ) are required for severe hazards.
- Other devices like DCVAs or PVBs are for lesser hazards or specific applications.
Memory trick: Hazard severe, RPZ is clear.