Journeyman Plumbers Exam Backflow Prevention 2 — Questions and Answers
Question 1: Which backflow preventer is required when a garden hose is connected to a boiler drain valve on a potable water system?
- Double check valve assembly
- Reduced pressure zone (RPZ) assembly
- Atmospheric vacuum breaker (AVB) (Correct answer)
- Pressure vacuum breaker (PVB)
Correct answer: Atmospheric vacuum breaker (AVB)
An atmospheric vacuum breaker is suitable for hose bibb connections on potable water systems where there is no continuous pressure downstream.
Question 2: A cross-connection is best defined as:
- A fitting used to join pipes at 90-degree angles
- Any physical connection between a potable and non-potable water supply (Correct answer)
- A valve that allows flow in only one direction
- A pipe that crosses another pipe in a wall
Correct answer: Any physical connection between a potable and non-potable water supply
A cross-connection is any physical link between a potable water supply and a potential source of contamination or pollution.
Question 3: What is the minimum height above the flood level rim that a pressure vacuum breaker (PVB) must be installed?
- 6 inches
- 12 inches (Correct answer)
- 18 inches
- 24 inches
Correct answer: 12 inches
A pressure vacuum breaker must be installed a minimum of 12 inches above the highest downstream outlet or flood level rim.
Question 4: Which of the following applications requires a reduced pressure zone (RPZ) backflow preventer?
- Lawn irrigation system with no chemical injection
- Hose bibb on an exterior wall
- Fire sprinkler system using antifreeze (Correct answer)
- Toilet fill valve
Correct answer: Fire sprinkler system using antifreeze
Fire sprinkler systems using antifreeze present a high-hazard condition requiring an RPZ because antifreeze is toxic if it enters the potable supply.
Question 5: The check valves inside a double check valve assembly (DCVA) must each be capable of holding against how much static pressure?
- 5 psi
- 10 psi (Correct answer)
- 15 psi
- 25 psi
Correct answer: 10 psi
Each check valve in a DCVA must independently hold against a minimum of 10 psi of backpressure.
Question 6: Back-siphonage is caused by:
- Excess pressure in the downstream piping
- A negative pressure (vacuum) on the supply side (Correct answer)
- A blocked check valve
- High velocity flow in the main
Correct answer: A negative pressure (vacuum) on the supply side
Back-siphonage occurs when a negative or sub-atmospheric pressure develops in the supply piping, drawing non-potable water backward.
Question 7: Which type of backflow is caused by downstream pressure exceeding supply pressure?
- Back-siphonage
- Thermal expansion backflow
- Back-pressure backflow (Correct answer)
- Vapor lock backflow
Correct answer: Back-pressure backflow
Back-pressure backflow occurs when downstream pressure (from pumps, boilers, or elevated tanks) exceeds the supply pressure.
