Master Plumber Exam Backflow Prevention and Safety 5 — Questions and Answers
Question 1: A cross-connection survey identifies a dental office with a unit that has water lines running into patient rinse bowls. What level of hazard does this represent?
- Non-hazard — no protection needed
- Low hazard — double check valve required
- High hazard — RPZ or air gap required (Correct answer)
- Medium hazard — pressure vacuum breaker required
Correct answer: High hazard — RPZ or air gap required
Dental equipment can introduce biological and chemical contaminants into the water supply, classifying it as a high-hazard connection requiring RPZ or air gap protection.
Question 2: Which standard governs the testing and certification of backflow prevention assembly testers in the United States?
- ASSE 5010-2019 (Correct answer)
- ASSE 1013
- AWWA M14
- USC FCCCHR
Correct answer: ASSE 5010-2019
ASSE 5010-2019 (formerly 5000) is the professional qualifications standard for backflow prevention assembly testers in the US.
Question 3: An irrigation system services both a potable-water zone and a reclaimed water zone on the same property. Which code requirement applies to the potable water supply connection?
- A single check valve is sufficient since the system is on private property
- An RPZ assembly is required to prevent reclaimed water from entering the potable supply (Correct answer)
- No protection is needed if reclaimed water is treated to secondary standards
- A double check valve is sufficient because reclaimed water is not a high hazard
Correct answer: An RPZ assembly is required to prevent reclaimed water from entering the potable supply
Reclaimed (recycled) water is considered a high-hazard contaminant; an RPZ assembly is required on the potable supply connection to prevent cross-contamination.
Question 4: A hose connection vacuum breaker (HCVB) is designed to protect against which specific hazard?
- Backpressure from a boiler system
- Backsiphonage through a garden hose connected to a potable hose bib (Correct answer)
- High-hazard chemical cross-connections in industrial settings
- Thermal expansion in a closed plumbing system
Correct answer: Backsiphonage through a garden hose connected to a potable hose bib
An HCVB (ASSE 1011) is a simple device that screws onto a hose bib to prevent backsiphonage when a hose is submerged in a non-potable source.
Question 5: When installing an RPZ assembly in a pit or vault, what is the most critical code concern?
- The assembly must be oriented vertically at all times
- The vault must be classified as a confined space and the relief valve must not be submerged (Correct answer)
- The assembly must be wrapped in insulation to prevent freezing
- The vault must be painted red to indicate high-hazard use
Correct answer: The vault must be classified as a confined space and the relief valve must not be submerged
Installing an RPZ in a pit creates confined-space hazards for maintenance workers and risks submerging the relief valve in water, which would allow contamination to enter the zone.
Question 6: Which condition would cause a double check valve assembly (DCVA) to fail a field test?
- The inlet shut-off valve requires more than one turn to close
- Either check valve fails to hold against a closed downstream condition (Correct answer)
- The assembly is installed more than 5 feet above grade
- The test cock fitting is a different brand than the assembly body
Correct answer: Either check valve fails to hold against a closed downstream condition
A DCVA fails the field test if either check valve leaks when pressure is applied in the reverse direction, indicating the check is fouled or worn.
Question 7: Under the International Plumbing Code (IPC), which type of backflow protection is required for a water connection to a solar thermal heating system that uses antifreeze fluid?
- Hose connection vacuum breaker (ASSE 1011)
- Double check valve assembly (DCVA)
- Reduced pressure zone (RPZ) assembly (Correct answer)
- Pressure vacuum breaker (PVB)
Correct answer: Reduced pressure zone (RPZ) assembly
Antifreeze is a toxic chemical, classifying a solar thermal system using it as a high-hazard cross-connection requiring an RPZ assembly on the potable water supply.
Master Plumber Exam Backflow Prevention and Safety 5
A cross-connection survey identifies a dental office with a unit that has water lines running into patient rinse bowls.
What level of hazard does this represent?