Master Plumber Exam Backflow Prevention and Safety 3 — Questions and Answers
Question 1: An RPZ assembly relief valve is discharging water continuously during normal system operation. What is the most likely cause?
- Inlet pressure is too low (Correct answer)
- The first check valve is fouled or leaking
- The second check valve is stuck open
- Downstream pressure exceeds supply pressure
Correct answer: Inlet pressure is too low
If the first check valve fails to hold, the pressure in the zone drops below the inlet, causing the relief valve to open and discharge water continuously.
Question 2: Which backflow prevention method provides the highest level of protection for a potable water supply?
- Pressure vacuum breaker
- Double check valve assembly
- Air gap (Correct answer)
- Reduced pressure zone assembly
Correct answer: Air gap
An air gap is the only backflow prevention method that provides a complete physical separation between the supply and potential contaminant, making it the most reliable protection.
Question 3: Under ASSE 1013, what is the minimum relief valve opening differential pressure for a reduced pressure zone assembly?
- 1 psi
- 2 psi (Correct answer)
- 5 psi
- 10 psi
Correct answer: 2 psi
ASSE 1013 requires the RPZ relief valve to open when the differential pressure across the first check drops to 2 psi or less, protecting the zone.
Question 4: A booster pump on a recirculating fire suppression system is connected to the potable water main. Which device is required at the connection?
- Atmospheric vacuum breaker (AVB)
- Double check detector assembly (DCDA) (Correct answer)
- Pressure vacuum breaker (PVB)
- Hose bib vacuum breaker
Correct answer: Double check detector assembly (DCDA)
Fire suppression systems with pumps represent a potential backpressure hazard requiring a double check detector assembly to protect the potable supply.
Question 5: How often must testable backflow prevention assemblies typically be tested after initial installation under most US jurisdictions?
- Every month
- Every 6 months
- Annually (Correct answer)
- Every 5 years
Correct answer: Annually
Most US jurisdictions require annual testing of all testable backflow prevention assemblies (RPZ, DCVA, PVB) by a certified tester.
Question 6: Which statement is TRUE about an atmospheric vacuum breaker (AVB)?
- It can be installed downstream of a shut-off valve
- It must be installed at least 6 inches above the highest downstream outlet (Correct answer)
- It can be tested with standard backflow test equipment
- It can remain under continuous pressure indefinitely
Correct answer: It must be installed at least 6 inches above the highest downstream outlet
An AVB must be installed at least 6 inches above the highest point of the downstream system to function correctly and prevent siphonage.
Question 7: What federal law mandates that public water systems protect their distribution systems from contamination caused by cross-connections?
- The Clean Water Act (CWA)
- The Safe Drinking Water Act (SDWA) (Correct answer)
- The National Environmental Policy Act (NEPA)
- The Resource Conservation and Recovery Act (RCRA)
Correct answer: The Safe Drinking Water Act (SDWA)
The Safe Drinking Water Act (SDWA) requires public water systems to implement cross-connection control programs to protect potable water quality.
Master Plumber Exam Backflow Prevention and Safety 3
An RPZ assembly relief valve is discharging water continuously during normal system operation.
What is the most likely cause?