Backflow Prevention Practice Exam

In which situation is an air gap considered insufficient?

1. Near a water heater

2. Above a sink

3. Adjacent to a water treatment plant

4. Close to a sanitary drain

The correct answer is: Close to a sanitary drain

An air gap is a crucial component in backflow prevention and is defined as the physical vertical distance between the highest point of a liquid in a container and the lowest point of a potential backflow source. In situations close to a sanitary drain, an air gap is considered insufficient because the proximity increases the possibility of contamination from wastewater entering the potable water supply. If a fixture with a proper air gap is too close to a sanitary drain, there is a risk that splashing or siphoning could cause backflow and compromise the drinking water. In contrast, a water heater, sink, or water treatment plant typically does not present the same immediate risk of contamination as they are designed to keep water separate from potential backflow sources. The effectiveness of an air gap diminishes when the distance to a sanitary drain is not adequate, highlighting the critical need for a sufficient air gap that complies with regulations to ensure safe drinking water.