Rhode Island Journeyman Plumber Practice Exam

What is needed to prevent backflow in plumbing systems?

1. Pressure gauge

2. Vent pipe

3. Air gap

4. Inline filter

The correct answer is: Air gap

To prevent backflow in plumbing systems, an air gap is essential. An air gap is a physical separation that ensures there is no direct connection between the potable (drinkable) water supply and potential contaminants in non-potable water. This separation creates a barrier that prevents the reverse flow of water, which can occur due to changes in pressure or system malfunctions. For example, when water from a sink drains into a sewer system, without proper backflow prevention measures like an air gap, contaminated water could potentially siphon back into the potable water supply, posing serious health risks. The air gap effectively breaks this connection and is considered one of the most reliable methods for backflow prevention. In contrast, while elements like pressure gauges, vent pipes, and inline filters play essential roles in plumbing systems, they do not provide the same level of physical separation necessary to prevent backflow. A pressure gauge monitors system pressure, a vent pipe facilitates airflow and prevents vacuum conditions, and an inline filter removes particulates but does not prevent the reversal of flow.