ABC Backflow Prevention Assembly 2 — Questions and Answers
Question 1: Which backflow prevention assembly is required when the downstream piping may be subject to back-pressure AND the supply may be shut off while the downstream system remains pressurized?
- Atmospheric vacuum breaker
- Pressure vacuum breaker
- Double check valve assembly
- Reduced pressure principle assembly (Correct answer)
Correct answer: Reduced pressure principle assembly
The reduced pressure principle (RP) assembly is required for high-hazard conditions involving back-pressure scenarios where the downstream system may remain pressurized.
Question 2: What does the term 'backsiphonage' refer to in backflow prevention?
- Downstream pressure exceeding supply pressure
- Negative pressure in the supply line drawing contaminants back (Correct answer)
- A failure of both check valves simultaneously
- Pressure buildup in the distribution system
Correct answer: Negative pressure in the supply line drawing contaminants back
Backsiphonage occurs when negative (subatmospheric) pressure in the supply line creates a siphon that pulls contaminants backward into the potable water system.
Question 3: A double check valve assembly (DCVA) is appropriate for which hazard classification?
- High hazard only
- Low hazard only (Correct answer)
- Both high and low hazard
- Health hazard only
Correct answer: Low hazard only
The DCVA is approved for low-hazard (non-health) cross-connections where there is no risk of contaminating potable water with toxic or health-threatening substances.
Question 4: During an RP assembly field test, if the #1 check valve shows a differential pressure reading below the minimum acceptable threshold, this indicates:
- The relief valve is functioning correctly
- The #1 check valve is fouled or failing (Correct answer)
- The #2 check valve needs replacement
- The assembly is operating normally
Correct answer: The #1 check valve is fouled or failing
A #1 check valve differential reading below the minimum threshold (typically 5 psi) indicates the check valve is not holding properly and may be fouled or failing.
Question 5: Which of the following cross-connections would be classified as a HIGH hazard?
- Irrigation system using potable water only
- Booster pump connection on a residential building
- Chemical injection system connected to a cooling tower (Correct answer)
- Fire sprinkler system with no additives
Correct answer: Chemical injection system connected to a cooling tower
A chemical injection system connected to a cooling tower presents a high hazard because toxic chemicals or biological contaminants could enter the potable supply.
Question 6: An air gap is considered the most reliable form of backflow protection because:
- It uses mechanical components that can be tested annually
- It is the least expensive option to install
- It provides a physical separation requiring no mechanical parts to fail (Correct answer)
- It is approved only for industrial applications
Correct answer: It provides a physical separation requiring no mechanical parts to fail
An air gap requires no mechanical components, so there are no parts to fail or foul, making it the most reliable backflow protection method.
Question 7: When testing a pressure vacuum breaker (PVB), the tester opens the #2 test cock and the air inlet valve opens. This indicates:
- The check valve has failed
- The air inlet is functioning properly by opening under test conditions (Correct answer)
- The PVB needs immediate replacement
- Back-pressure exists downstream
Correct answer: The air inlet is functioning properly by opening under test conditions
The air inlet valve on a PVB should open when the body of the assembly is depressurized during testing, which is the normal and expected response.
ABC Backflow Prevention Assembly 2
Which backflow prevention assembly is required when the downstream piping may be subject to back-pressure AND the supply may be shut off while the downstream system remains pressurized?