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.
Journeyman Plumbers Exam Backflow Prevention 4
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?