Illinois Plumbing Code Practice Exam 2025 – All-in-One Guide for Exam Success!

The correct choice, Reduced Pressure Principle, is required for water supply inlets to kidney dialysis equipment because it provides the highest level of protection against backflow, especially in applications where health and safety are critical. Kidney dialysis equipment is susceptible to contamination due to the introduction of water into the patient's bloodstream. The Reduced Pressure Principle backflow preventer is designed to create a pressure differential that effectively prevents water from flowing back into the potable supply, thus safeguarding against potential contaminants that could affect patient health.

This type of assembly includes two independently acting check valves and a pressure relief valve located between them, which constantly monitors the system pressure. If the pressures drop in the supply line, the pressure relief valve opens to release that pressure to the atmosphere, preventing backflow. This feature is particularly important for sensitive medical equipment like dialysis machines, where any reversal of flow could lead to serious health risks.

The other types of backflow preventers do not offer the same level of protection required for this critical application. For example, an Atmospheric Vacuum Breaker provides basic protection but is not suitable for continuous pressure situations inherent in medical applications. Similarly, while a Pressure Vacuum Breaker can provide some level of protection, it does not offer the same fail-safety as the Reduced Pressure Principle assembly