Journeyman Plumbers Exam Backflow Prevention 4 — Questions and Answers
Question 1: An air gap is the physical separation between a water supply outlet and the flood level rim of a receiving vessel. What is the minimum air gap for a 1-inch supply pipe?
- 1 inch
- 1.5 inches
- 2 inches (Correct answer)
- 3 inches
Correct answer: 2 inches
The minimum air gap is twice the effective opening of the supply pipe, so a 1-inch pipe requires at least a 2-inch air gap.
Question 2: Which backflow prevention method provides the highest level of protection for a potable water supply?
- Double check valve assembly
- Pressure vacuum breaker
- Air gap (Correct answer)
- Reduced pressure zone assembly
Correct answer: Air gap
An air gap is the only method that provides complete physical separation between the supply and potential contamination, making it the highest level of protection.
Question 3: A spill-resistant pressure vacuum breaker (SVB) differs from a standard PVB in that it:
- Does not require a minimum height above the highest outlet
- Can be installed indoors because it contains the water discharged during operation (Correct answer)
- Provides RPZ-level protection against backpressure
- Has three check valves instead of two
Correct answer: Can be installed indoors because it contains the water discharged during operation
The spill-resistant PVB contains a specially designed body that prevents the relief discharge from spilling, making it suitable for indoor installations.
Question 4: On a fire sprinkler system connected to the potable supply, the isolation valves on the backflow preventer assembly must be which type?
- Ball valves that open and close with a quarter turn
- Indicating-type valves (OS&Y or butterfly with tamper switch) (Correct answer)
- Gate valves without locking devices
- Check valves that allow flow in one direction only
Correct answer: Indicating-type valves (OS&Y or butterfly with tamper switch)
Fire system isolation valves must be indicating-type (such as OS&Y gate valves or supervised butterfly valves) so it can be visually confirmed whether they are open or closed.
Question 5: If a reduced pressure zone assembly's relief port is discharging continuously during normal system operation, this most likely indicates:
- The downstream demand is exceeding supply pressure
- A failed or fouled check valve allowing pressure differential to drop below 2 psi (Correct answer)
- The device is functioning normally and expelling excess pressure
- The supply pressure is too high for the assembly rating
Correct answer: A failed or fouled check valve allowing pressure differential to drop below 2 psi
Continuous discharge from the relief port indicates that the differential pressure across the first check has dropped below the 2 psi threshold, typically due to a failed or debris-fouled check valve.
Question 6: Which installation configuration is acceptable for a pressure vacuum breaker (PVB)?
- Installed downstream of a shut-off valve that can be closed while PVB is under pressure
- Installed upstream of any chemical injection points (Correct answer)
- Installed in a pit or below grade where flooding can occur
- Installed at the same elevation as the highest downstream sprinkler head
Correct answer: Installed upstream of any chemical injection points
The PVB must always be installed upstream of any chemical injection or potential contamination source to provide protection.
Question 7: What organization publishes the Uniform Plumbing Code (UPC) that governs backflow prevention requirements in many US jurisdictions?
- International Association of Plumbing and Mechanical Officials (IAPMO) (Correct answer)
- American Society of Sanitary Engineering (ASSE)
- American Water Works Association (AWWA)
- National Fire Protection Association (NFPA)
Correct answer: International Association of Plumbing and Mechanical Officials (IAPMO)
The Uniform Plumbing Code (UPC) is published by IAPMO and is adopted by many western US states as the governing plumbing standard.
