AWWA Cross-Connection Control and Backflow Prevention 2 — Questions and Answers
Question 1: How is an air gap defined as a backflow prevention method?
- A space maintained between two check valves inside a backflow preventer assembly
- An unobstructed vertical separation between the water supply outlet and the flood level rim of a receiving vessel (Correct answer)
- A vacuum created in the supply line to physically prevent backflow
- A vent installed on the top of elevated water storage tanks
Correct answer: An unobstructed vertical separation between the water supply outlet and the flood level rim of a receiving vessel
An air gap is a physical, unobstructed vertical distance between the lowest opening of a water supply outlet and the flood level rim of a receiving vessel, ensuring no physical connection exists.
Question 2: Which AWWA standard covers double check valve backflow prevention assemblies?
- AWWA C200
- AWWA C510 (Correct answer)
- AWWA C900
- AWWA C150
Correct answer: AWWA C510
AWWA C510 is the standard specifically addressing double check valve backflow prevention assemblies, covering design, materials, and performance requirements.
Question 3: What does 'degree of hazard' mean in a cross-connection control program?
- The measured pressure differential between the supply and downstream systems
- The classification of the severity of potential contamination if a backflow event occurs (Correct answer)
- The physical distance between a water main and a potential contamination source
- The volumetric flow rate that could pass through a cross-connection during backflow
Correct answer: The classification of the severity of potential contamination if a backflow event occurs
Degree of hazard classifies cross-connections as high hazard (health or toxic hazard) or low hazard (non-health or pollutant hazard) based on the potential severity of contamination.
Question 4: Where must an atmospheric vacuum breaker (AVB) be installed relative to control valves?
- Upstream of all control valves so it is always under supply pressure
- Downstream of the last control valve where it will not be under continuous pressure (Correct answer)
- At the water meter to protect the entire premise plumbing system
- On the main supply line entering a building before any branch connections
Correct answer: Downstream of the last control valve where it will not be under continuous pressure
An AVB must be installed downstream of the last control valve and must not be subject to continuous water pressure, as it is designed only for intermittent use and will fail if held open under constant pressure.
Question 5: What is the minimum required air gap distance between a water supply outlet and the flood level rim of the receiving vessel?
- Equal to the pipe inside diameter or 1 inch, whichever is greater
- Twice the pipe inside diameter or 1 inch, whichever is greater (Correct answer)
- Three times the pipe inside diameter or 1 inch, whichever is greater
- Twice the pipe inside diameter or 2 inches, whichever is greater
Correct answer: Twice the pipe inside diameter or 1 inch, whichever is greater
The minimum air gap must be twice the effective inside diameter of the supply pipe, but never less than 1 inch, to provide adequate separation under all flow conditions.
Question 6: Which type of premises typically requires the highest level of backflow protection at the utility service connection?
- Single-family residential homes with standard plumbing
- Fire suppression systems that use chemical additives such as antifreeze or foam concentrates (Correct answer)
- Commercial car washes with recycled water rinse systems
- Restaurants with standard dishwashing equipment
Correct answer: Fire suppression systems that use chemical additives such as antifreeze or foam concentrates
Fire suppression systems using chemical additives (antifreeze, foam concentrates) represent a high-hazard cross-connection requiring an RPZ assembly at the service connection because chemicals could be toxic if backsiphoned into the potable supply.
Question 7: What is the primary purpose of a cross-connection control survey conducted by the water utility?
- To measure and record water pressure at all points on a customer's premises
- To identify and evaluate actual or potential cross-connections so appropriate backflow prevention can be required (Correct answer)
- To test the flow rate through customer meters for billing accuracy
- To assess the structural integrity and material composition of customer service lines
Correct answer: To identify and evaluate actual or potential cross-connections so appropriate backflow prevention can be required
A cross-connection control survey is conducted to identify and evaluate all actual or potential cross-connections on customer premises so the utility can require installation of appropriate backflow prevention devices.
AWWA Cross-Connection Control and Backflow Prevention 2
How is an air gap defined as a backflow prevention method?