Which backflow prevention device is used in plumbing to prevent backflow of non-potable liquids into the drinking water system?

Which backflow prevention device is used in plumbing to prevent backflow of non-potable liquids into the drinking water system?

• A. Check Valve
• B. Reduced Pressure Zone
• C. Atmospheric Vacuum Breaker
• D. Pressure Vacuum Breaker

Answer: (C)

Backflow prevention is about stopping the flow of non-potable liquids back into the drinking water supply when pressure in the piping changes. An atmospheric vacuum breaker protects against back-siphonage by venting to the atmosphere. When pressure in the potable line drops, the vent opens and air enters the line, breaking the siphon and preventing contaminated water from being drawn back into the drinking system. This simple mechanism is well suited for outdoor or irrigation applications where siphonage is the primary concern, and it’s relatively inexpensive and easy to install. It should be placed where it won’t be subjected to backpressure, and it’s not intended for scenarios where backpressure could occur. Other devices either rely on a one-way valve alone, which doesn’t guard against siphon-related backflow, or are more robust and designed for backpressure or higher-risk cross-connections (such as reduced pressure zone assemblies or pressure vacuum breakers). The atmospheric vacuum breaker is chosen here because it directly addresses back-siphonage from non-potable sources into the drinking water supply in typical, lower-risk applications.

Backflow prevention is about stopping the flow of non-potable liquids back into the drinking water supply when pressure in the piping changes. An atmospheric vacuum breaker protects against back-siphonage by venting to the atmosphere. When pressure in the potable line drops, the vent opens and air enters the line, breaking the siphon and preventing contaminated water from being drawn back into the drinking system. This simple mechanism is well suited for outdoor or irrigation applications where siphonage is the primary concern, and it’s relatively inexpensive and easy to install. It should be placed where it won’t be subjected to backpressure, and it’s not intended for scenarios where backpressure could occur.

Other devices either rely on a one-way valve alone, which doesn’t guard against siphon-related backflow, or are more robust and designed for backpressure or higher-risk cross-connections (such as reduced pressure zone assemblies or pressure vacuum breakers). The atmospheric vacuum breaker is chosen here because it directly addresses back-siphonage from non-potable sources into the drinking water supply in typical, lower-risk applications.