Rhode Island Journeyman Plumber Practice Exam

How is backflow for an automatic clothes washer prevented?

1. Check Valve

2. Air Break

3. Vacuum Breaker

4. Double Check Valve

The correct answer is: Air Break

To prevent backflow in an automatic clothes washer, an air break is employed. This system effectively creates a physical separation between the potential contamination source and the potable water supply. By installing an air break, which typically consists of a standpipe or a gap between the drain hose of the washer and the drain itself, it guarantees that even in situations where negative pressure occurs, water cannot siphon back into the washer from the drain. The method of an air gap is particularly important because it is a simple and reliable way to protect against backflow, ensuring that dirty water does not mix with clean water from the washing machine. This practice aligns with plumbing codes and regulations to maintain a safe drinking water supply by preventing any cross-contamination. Other options, while they serve important functions in plumbing systems, do not specifically create the necessary protection against backflow for a clothes washer as effectively as an air break does. For instance, check valves and double check valves are often used in different contexts for backflow prevention but are more suited for systems where the risks of backflow are primarily due to pressure changes in closed systems rather than open drainage. A vacuum breaker does provide backflow prevention as well, but it relies on pressure differentials and does not establish the physical separation inherent