AWWA Cross-Connection Control and Backflow Prevention 1 — Questions and Answers
Question 1: What is a cross-connection in a water distribution system?
- A pipe junction where two main distribution lines meet
- Any actual or potential connection between a potable water supply and a source of contamination (Correct answer)
- A valve assembly used to regulate flow between two separate water systems
- A fitting used to connect pipes of different diameters
Correct answer: Any actual or potential connection between a potable water supply and a source of contamination
A cross-connection is any actual or potential connection between the potable water supply and any source of contamination or pollution that could allow backflow to occur.
Question 2: What is backflow in a water distribution context?
- The normal forward flow of water through a pressurized distribution system
- The undesirable reversal of flow of water or other substances into the potable water supply (Correct answer)
- The overflow of water from an elevated storage tank during high demand
- A pressure surge that occurs when a valve is rapidly closed
Correct answer: The undesirable reversal of flow of water or other substances into the potable water supply
Backflow is the undesirable reversal of flow of water or other substances into the potable water distribution system, potentially introducing contaminants.
Question 3: What are the two recognized types of backflow?
- Laminar backflow and turbulent backflow
- Pressure backflow and vacuum backflow
- Backsiphonage and backpressure (Correct answer)
- Hydraulic backflow and pneumatic backflow
Correct answer: Backsiphonage and backpressure
The two types of backflow are backsiphonage (caused by negative pressure in the supply line) and backpressure (caused by downstream pressure exceeding supply pressure).
Question 4: Which backflow prevention device provides the highest level of protection against contamination?
- Pressure vacuum breaker (PVB)
- Double check valve assembly (DCVA)
- Reduced pressure principle assembly (RPZ) (Correct answer)
- Atmospheric vacuum breaker (AVB)
Correct answer: Reduced pressure principle assembly (RPZ)
The reduced pressure principle (RPZ) assembly provides the highest mechanical protection because it has two independent check valves plus a relief valve that opens if either check valve fails.
Question 5: What pressure condition causes backsiphonage?
- Excessive downstream pressure from a booster pump
- Negative or sub-atmospheric pressure developing in the supply line (Correct answer)
- Thermal expansion in a closed plumbing system
- Elevation pressure differences between water mains
Correct answer: Negative or sub-atmospheric pressure developing in the supply line
Backsiphonage occurs when negative or sub-atmospheric pressure develops in the supply piping, creating a siphon effect that pulls water backward through the cross-connection.
Question 6: According to AWWA guidelines, how frequently should backflow prevention assemblies be tested?
- Every five years
- Every three years
- At least annually (Correct answer)
- Every six months
Correct answer: At least annually
AWWA recommends that backflow prevention assemblies be tested at least once per year by a certified tester to verify all components are functioning correctly.
Question 7: Which of the following is NOT an approved backflow prevention method for a high-hazard cross-connection?
- Reduced pressure principle assembly (RPZ)
- Air gap separation
- Single check valve (Correct answer)
- Reduced pressure detector assembly (RPDA)
Correct answer: Single check valve
A single check valve provides only minimal mechanical protection with no redundancy or relief mechanism and is not approved for high-hazard (health-hazard) cross-connections.
AWWA Cross-Connection Control and Backflow Prevention 1
What is a cross-connection in a water distribution system?