ABC ABC Cross-Connection Control and Monitoring 1 — Questions and Answers
Question 1: What is a cross-connection in a potable water system?
- A link between a potable supply and a potential source of contamination (Correct answer)
- A pipe fitting that joins two different pipe materials
- A meter connection between two service lines
- A bypass valve around a pressure reducing valve
Correct answer: A link between a potable supply and a potential source of contamination
A cross-connection is any physical connection between a potable water supply and a non-potable source that could allow contamination to enter the drinking water.
Question 2: What phenomenon causes backflow from a high-pressure non-potable source into the potable water system?
- Back-pressure backflow (Correct answer)
- Backsiphonage
- Negative pressure surge
- Hydraulic gradient reversal
Correct answer: Back-pressure backflow
Back-pressure backflow occurs when downstream pressure exceeds supply pressure, forcing non-potable water backward into the potable system.
Question 3: Which backflow preventer provides the highest level of protection and is required for high-hazard cross-connections?
- Reduced Pressure Zone (RPZ) assembly (Correct answer)
- Double check valve assembly
- Atmospheric vacuum breaker
- Pressure vacuum breaker
Correct answer: Reduced Pressure Zone (RPZ) assembly
The Reduced Pressure Zone (RPZ) assembly provides the highest level of backflow protection and is required for high-hazard applications such as chemical injection systems.
Question 4: What type of backflow occurs when a drop in supply pressure creates a vacuum that siphons contaminants into the potable water system?
- Backsiphonage (Correct answer)
- Back-pressure backflow
- Hydraulic shock
- Water hammer
Correct answer: Backsiphonage
Backsiphonage is caused by negative pressure (vacuum) in the supply line that draws contaminants backward into the potable system.
Question 5: Under the USC Model Cross-Connection Control Program, which device is approved for protection against backsiphonage only and must not be installed under continuous pressure?
- Atmospheric vacuum breaker (Correct answer)
- Double check valve assembly
- Reduced Pressure Zone assembly
- Pressure vacuum breaker
Correct answer: Atmospheric vacuum breaker
The atmospheric vacuum breaker (AVB) is approved only for backsiphonage conditions and must not be subjected to continuous downstream pressure.
Question 6: What is the minimum air gap required between a potable water supply outlet and the flood rim of a receiving vessel, per ASME/ANSI standards?
- Two times the diameter of the supply pipe or 1 inch, whichever is greater (Correct answer)
- One pipe diameter above the flood rim
- Six inches regardless of pipe size
- Four times the pipe diameter
Correct answer: Two times the diameter of the supply pipe or 1 inch, whichever is greater
ASME A112.1.2 specifies that the air gap must be at least twice the effective opening diameter or 1 inch, whichever is greater.
ABC ABC Cross-Connection Control and Monitoring 1
What is a cross-connection in a potable water system?