Which device helps prevent backflow contamination in a cold water system?

• A. A pressure reducing valve.
• B. A backflow-prevention device.
• C. An air vent.
• D. A check valve.

Answer: (B)

Preventing reverse flow from a potentially contaminated source is essential to keep the cold-water supply safe. A backflow-prevention device is designed specifically to stop water from flowing back into the potable system when pressure changes or cross-connections occur, protecting against both back-siphonage and back-pressure. The other options don’t provide that targeted protection: a pressure-reducing valve lowers pressure but doesn’t isolate the supply from backflow; an air vent just releases trapped air and has no backflow function; a simple check valve can block flow in one direction but may not prevent contamination in all scenarios and isn’t a complete backflow protection solution.