CIT - Certified Irrigation Technician Backflow Prevention Devices Questions and Answers — Questions and Answers
Question 1: An irrigation system is being installed at a commercial property where fertilizer will be injected into the mainline (chemigation). The local water purveyor has classified this as a high-hazard situation. Which of the following backflow prevention assemblies is required for this application?
- Double Check Valve Assembly (DCVA)
- Pressure Vacuum Breaker (PVB)
- Reduced Pressure Zone Assembly (RPZ) (Correct answer)
- Atmospheric Vacuum Breaker (AVB)
Correct answer: Reduced Pressure Zone Assembly (RPZ)
A Reduced Pressure Zone (RPZ) assembly is required for high-hazard applications, such as chemigation, where contaminants could be introduced into the potable water supply. It offers the highest level of protection by creating a zone of reduced pressure between two check valves and providing a relief valve to discharge water if backflow occurs.
Question 2: Backflow caused by a pressure increase in the downstream piping that is greater than the supply pressure is known as:
- Backsiphonage
- Backpressure (Correct answer)
- Water hammer
- Dynamic pressure
Correct answer: Backpressure
Backpressure is a condition where the pressure in the private water system (like an irrigation system with a booster pump or elevated piping) exceeds the pressure in the public water supply, potentially forcing non-potable water back into the supply. Backsiphonage is caused by a negative or reduced pressure in the supply line.
Question 3: Which of the following backflow prevention devices is unsuitable for applications where it would be under continuous pressure for more than 12 hours?
- Pressure Vacuum Breaker (PVB)
- Double Check Valve Assembly (DCVA)
- Reduced Pressure Zone Assembly (RPZ)
- Atmospheric Vacuum Breaker (AVB) (Correct answer)
Correct answer: Atmospheric Vacuum Breaker (AVB)
An Atmospheric Vacuum Breaker (AVB) is designed for backsiphonage protection only and must be installed on the discharge side of the last control valve. It is not designed to be under continuous pressure for more than a 12-hour period, as the internal components can fail or stick, rendering it ineffective.
Question 4: A technician is installing a Double Check Valve Assembly (DCVA) in a below-grade valve box. What is a critical installation requirement for this scenario?
- It must be installed at least 12 inches above the highest sprinkler head.
- The valve box must have adequate drainage to prevent the device from being submerged. (Correct answer)
- It must always be installed in a vertical orientation.
- It requires an air gap separation equal to twice the pipe diameter.
Correct answer: The valve box must have adequate drainage to prevent the device from being submerged.
While Double Check Valve Assemblies can be installed below grade, it is critical that the enclosure has proper drainage. If the device becomes submerged in potentially contaminated ground water, a cross-connection can occur through the test cocks, defeating the purpose of the device.
Question 5: The component of a Reduced Pressure Zone (RPZ) assembly that opens to discharge water to the atmosphere during a backflow condition is called the:
- Inlet shutoff valve
- First check valve
- Relief valve (Correct answer)
- Test cock #2
Correct answer: Relief valve
The relief valve is the key component that differentiates an RPZ from a DCVA. It is located in the 'zone' between the two check valves and is designed to open and discharge water if the pressure differential across the first check valve drops to a certain point, indicating a potential backflow condition. This ensures the contaminated water does not enter the potable supply.
Question 6: Which of the following statements correctly differentiates a Pressure Vacuum Breaker (PVB) from a Double Check Valve Assembly (DCVA)?
- A PVB protects against backpressure, while a DCVA only protects against backsiphonage.
- A DCVA must be installed above the highest outlet, while a PVB can be installed below grade.
- A PVB is suitable for high-hazard applications, while a DCVA is for low-hazard only.
- A PVB protects against backsiphonage only, while a DCVA protects against both backsiphonage and backpressure. (Correct answer)
Correct answer: A PVB protects against backsiphonage only, while a DCVA protects against both backsiphonage and backpressure.
A Pressure Vacuum Breaker (PVB) uses an air inlet to break a vacuum, making it effective only against backsiphonage. A Double Check Valve Assembly (DCVA) uses two independent check valves and can prevent backflow caused by either backsiphonage or backpressure, making it suitable for a wider range of hydraulic conditions (though only for low-hazard applications).
CIT - Certified Irrigation Technician Backflow Prevention Devices Questions and Answers
An irrigation system is being installed at a commercial property where fertilizer will be injected into the mainline (chemigation).
The local water purveyor has classified this as a high-hazard situation.
Which of the following backflow prevention assemblies is required for this application?