Backflow prevention devices are used to prevent contamination of potable water from non-potable sources. Which situation describes why such devices are needed?

• A. Water hammer
• B. Backsiphonage due to negative pressure
• C. Corrosion
• D. Sediment buildup

Answer: (B)

Backflow prevention devices protect drinking water by blocking any reverse movement of water into the potable supply when pressure conditions in the system change. The situation described—backsiphonage due to negative pressure—occurs when supply pressure drops below the pressure in a connected non-potable source, creating a suction that can pull water back into the clean water system. A backflow prevention device serves as a barrier to stop that backward flow, preventing contaminants from non-potable sources from entering the distribution system. The other options don’t describe why these devices are needed: water hammer is a pressure surge that can damage pipes, not specifically a contamination risk from reverse flow; corrosion and sediment buildup affect pipe integrity or clarity but don’t inherently cause backflow contamination.