What does a flow check prevent?

• A. Air entrapment
• B. Overheating
• C. Air binding
• D. Backflow into the supply

Answer: (D)

The main idea here is preventing contaminants from entering the drinking water by stopping reverse flow. A flow check functions as a one-way valve that lets water move through in the intended direction but closes if pressure on the downstream side tries to push water back toward the supply. This stops backflow, protecting the potable water supply from siphoning or contamination when equipment shuts down or pressures fluctuate. Air entrapment and air binding involve air in the system and can affect pump performance, not backflow prevention. Overheating is a thermal issue unrelated to flow direction.