Free Association of Boards of Certification Backflow Prevention Assembly Questions and Answers 1 — Questions and Answers
Question 1: What is the pressure at the base of a 100 foot high standpipe filled with water?
- 0.433 psi
- 2.31 psi
- 14.7 psi
- 43.3 psi (Correct answer)
Correct answer: 43.3 psi
The pressure at the base of a water column can be calculated using the formula: <br> Pressure (psi) = Height (ft)×0.433<br> <br> For a 100-foot high standpipe:<br> 100ft×0.433psi/ft=43.3psi <br> <br> This formula derives from the fact that 1 foot of water exerts approximately 0.433 psi of pressure due to gravity.
Question 2: A check valve in an approved backflow assembly must be...
- Resilient seated and loaded to the closed position (Correct answer)
- Resilient seated and loaded to the open position
- Hard seated and loaded to the open position
- Hard seated and loaded to the closed position
Correct answer: Resilient seated and loaded to the closed position
A check valve is designed to allow flow in one direction while preventing backflow. To ensure reliability and effectiveness, it must have a resilient seat (which provides a tight seal) and be spring-loaded to remain closed when not in use. This design helps to maintain system integrity and prevent contamination of potable water supplies.
Question 3: What are two types of backflow conditions?
- Backsiphonage and capillary action
- Backpressure and backsiphonage (Correct answer)
- Isolation and containment
- Potable and non-potable
Correct answer: Backpressure and backsiphonage
Backpressure: This occurs when the pressure in the downstream piping system exceeds the pressure in the supply line, causing water to flow backward. This can happen due to pumps or thermal expansion. <br> <br> Backsiphonage: This occurs when there is a negative pressure (vacuum) in the supply line, often due to a sudden drop in pressure (like a water main break), causing water to be siphoned back into the potable water system.
Question 4: A leaking check valve #2 of a reduced pressure assembly and backpressure may cause...
- Pressure regulator damage
- Check valve #1 to open
- Relief valve discharge (Correct answer)
- Disc compression
Correct answer: Relief valve discharge
In a reduced pressure backflow assembly, if check valve #2 leaks and backpressure is present, it can cause the pressure differential to drop. This situation activates the relief valve, which is designed to discharge water to prevent contamination from entering the potable supply. The relief valve functions as a safety mechanism to maintain system integrity.
Question 5: While testing check valve #2 of a reduced pressure backflow assembly under backpressure, what would be observed if the second check valve was fouled?
- Differential on the test kit and no discharge from the relief valve
- No differential on the test kit and discharge from the relief valve
- No differential on the test kit and no discharge from the relief valv
- Differential on the test kit and discharge from the relief valve (Correct answer)
Correct answer: Differential on the test kit and discharge from the relief valve
If check valve #2 is fouled (i.e., obstructed or malfunctioning), it would not effectively prevent backflow. During testing under backpressure, the test kit would show a pressure differential indicating that the check valve is not holding properly. Additionally, water would discharge from the relief valve, as it is designed to release excess pressure and prevent contamination, indicating that the assembly is not functioning correctly.
Free Association of Boards of Certification Backflow Prevention Assembly Questions and Answers 1
What is the pressure at the base of a 100 foot high standpipe filled with water?