What is the function of a backflow preventer?

• A. To monitor temperature
• B. Prevents reverse flow to protect potable water from contamination
• C. To provide structural support
• D. To regulate flow rate

Answer: (B)

Backflow preventers halt reverse flow into the potable water supply. Their job is to stop contaminated water from siphoning back into clean drinking water when pressure in the system drops or when there’s a cross-connection with sources like irrigation, boilers, or chemicals. By using mechanisms such as check valves and sometimes air gaps or relief paths, they block any backward movement of water, protecting health and safety. They don’t monitor temperature, provide structural support, or regulate how fast water flows, so those functions belong to other parts of the system.