Cross Connection Practice Exam

Backflow in a public water supply can be caused by:

1. Air pressure changes

2. Backpressure and Backsiphonage

3. Pumping variations

4. Temperature fluctuations

The correct answer is: Backpressure and Backsiphonage

Backflow in a public water supply occurs primarily due to two mechanisms: backpressure and backsiphonage. Backpressure happens when the pressure in a system connected to the public water supply exceeds the pressure in the water system itself. This often occurs in situations where a pump is used, or in high-rise buildings where water pressure can fluctuate due to elevation changes. When the pressure in a connected system rises above that of the supply, contaminated water can flow back into the public system. Backsiphonage, on the other hand, is a result of negative pressure or a vacuum that forms in the water supply system. This can occur during events like a water main break or when water is drawn from a hydrant or a large connection, creating a drop in pressure that causes the flow of water to reverse. This allows potentially contaminated water from sources near the supply system to be drawn back into the public water supply. While other factors like air pressure changes, pumping variations, and temperature fluctuations can influence water flow, they do not specifically cause backflow as directly or significantly as backpressure and backsiphonage do. Therefore, the identification of backpressure and backsiphonage as the primary causes of backflow reflects their critical role in maintaining safe