Which of the following describes the fundamental principle of a reduced pressure zone (RPZ) backflow preventer?

Question: Which of the following describes the fundamental principle of a reduced pressure zone (RPZ) backflow preventer?

Answer options: ✅ It maintains a pressure zone between two check valves that is lower than the supply pressure.

• It uses a single check valve to prevent backflow in one direction only.
• It creates a vacuum within the non-potable side to prevent back-siphonage.
• It automatically purifies contaminated water before it can enter the potable supply.

Correct answer: It maintains a pressure zone between two check valves that is lower than the supply pressure.

Explanation: An RPZ device utilizes two independently acting check valves with an automatically operated relief valve located between them. The pressure in the zone between the check valves is maintained at a pressure lower than the supply pressure, ensuring that if either check valve fails, the relief valve will open to discharge any backflow. It does not purify water, rely on a single check valve, or create a vacuum on the non-potable side.