Texas Commission on Environmental Quality (TCEQ). Class C Water License Exam

What is the TCEQ preferred method for cross connection control?

1. Physical backflow preventer

2. Double check valve

3. Physical air gap

4. Reduced pressure zone device

The correct answer is: Physical air gap

The preferred method for cross connection control according to TCEQ guidelines is the physical air gap. A physical air gap serves as a critical barrier that prevents contaminated water from entering the clean water supply. This method involves maintaining a vertical distance between the outlet of a potable water supply and the flood level rim of the receptacle receiving the water, thus eliminating any potential for backflow. An air gap is highly effective because it does not rely on any mechanical components, which can fail or malfunction, making it a foolproof solution against backflow. It provides complete separation, ensuring that no backpressure or siphoning can draw water back into the supply line from a potentially contaminated source. This physical separation is essential for protecting public health by preventing cross connections that could compromise the safety of drinking water. The other methods, while effective under certain circumstances, do not provide the same level of security as an air gap. For instance, a physical backflow preventer and reduced pressure zone device are mechanical devices that can fail under extreme conditions, and a double check valve, though useful, may still permit backflow if not properly maintained. Thus, the physical air gap remains the most reliable and preferred option for ensuring the integrity of the water supply system.