Journeyman Plumbers Exam Backflow Prevention 3 — Questions and Answers
Question 1: An RPZ assembly must be installed how far above the floor or ground to allow for drainage and testing?
- At least 6 inches
- At least 12 inches (Correct answer)
- At least 18 inches
- At least 24 inches
Correct answer: At least 12 inches
RPZ assemblies require a minimum of 12 inches of clearance above the floor to allow access for testing and to permit relief port drainage.
Question 2: Which backflow device is NOT acceptable for use under continuous supply pressure?
- Pressure vacuum breaker (PVB)
- Atmospheric vacuum breaker (AVB) (Correct answer)
- Double check valve assembly (DCVA)
- Reduced pressure zone (RPZ)
Correct answer: Atmospheric vacuum breaker (AVB)
Atmospheric vacuum breakers must not be subjected to continuous supply pressure exceeding 12 hours as it can hold the check open, defeating the device.
Question 3: What does the relief port on an RPZ assembly do during a backflow event?
- It closes to prevent backflow from reaching the supply
- It opens to discharge water and protect the supply line from contamination (Correct answer)
- It signals an alarm panel to shut the main valve
- It redirects flow through the second check valve
Correct answer: It opens to discharge water and protect the supply line from contamination
When the differential pressure drops below 2 psi, the relief valve opens to atmosphere, discharging water rather than allowing contaminated water to reach the supply.
Question 4: A plumber is installing a backflow preventer on a chemical injection system for a swimming pool. Which device is required?
- Atmospheric vacuum breaker
- Double check valve assembly
- Reduced pressure zone assembly (Correct answer)
- Simple hose bibb vacuum breaker
Correct answer: Reduced pressure zone assembly
Chemical injection systems represent a severe health hazard and require an RPZ assembly for the highest level of protection.
Question 5: How often must a testable backflow prevention assembly be tested after installation?
- Every 6 months
- Annually (Correct answer)
- Every 2 years
- Only at time of installation
Correct answer: Annually
Most jurisdictions following the USC model require testable backflow prevention assemblies to be tested annually by a certified tester.
Question 6: Which of the following is an example of a high-hazard cross-connection?
- A garden hose left in a bucket of soapy water
- A carbonated beverage dispenser connected to potable water (Correct answer)
- A lawn sprinkler system with no fertilizer injection
- A water softener bypass line
Correct answer: A carbonated beverage dispenser connected to potable water
Carbonated beverage dispensers create a high-hazard cross-connection because CO2 and syrup can be siphoned back into the potable supply.
Question 7: What is the purpose of the bypass valve on a backflow preventer assembly installed in a commercial building?
- To allow water to flow while the assembly is being tested or repaired (Correct answer)
- To provide an alternate path for backflow to discharge safely
- To reduce system pressure to an acceptable level
- To equalize pressure on both sides of the check valves
Correct answer: To allow water to flow while the assembly is being tested or repaired
A bypass with a backflow preventer allows the building to maintain water service while the primary assembly is taken offline for testing or maintenance.
