A plumber would use a ________ to prevent contamination to a potable water supply.

• A. Pressure Reducing Valve
• B. Ball Valve
• C. Check Valve
• D. Backflow Prevention Device

Answer: (D)

Preventing contamination of the potable water supply hinges on stopping any reverse flow that could pull contaminants into the system. A backflow prevention device does exactly that by blocking reverse flow and keeping water moving in one direction, which protects the clean water from potential cross-connections with contaminant sources such as irrigation systems, boilers, or chemical lines.

Why the other options don’t fit: a pressure reducing valve lowers downstream pressure but isn’t designed to stop backflow, so it won’t reliably protect against contamination. A ball valve is simply a shutoff and provides no protection against backflow. A check valve prevents reverse flow in a single pipe leg but doesn’t address backflow risks across a system or cross-connections, and it may not provide the required level of protection in all situations.

So, the device that prevents contamination of the potable water supply is a backflow prevention device.