Backflow occurs when:

Backflow occurs when:

• A. Water source pressure drops or a pump fails, causing pesticide to flow back into the water supply.
• B. Pesticide evaporates before reaching target.
• C. Pesticide adheres to plant surfaces.
• D. Air enters the tank during filling.

Answer: (A)

Backflow is the undesired reversal of flow where pesticide from the application system would be drawn back into the water supply due to a pressure change. When the water source pressure drops or the pump fails, the pressure in the water line can fall below the pressure inside the spray system, creating a siphon that pulls pesticide back into the water supply. That scenario matches the idea of backflow, making it the correct choice. Other options describe different issues—evaporation is loss to air, adhesion is sticking to plants, and air entering during filling relates to air problems in the tank, not a reversal of flow back into the water supply. To prevent backflow, use backflow prevention devices or an air gap, and avoid cross-connections between the water supply and the spray system.

Backflow is the undesired reversal of flow where pesticide from the application system would be drawn back into the water supply due to a pressure change. When the water source pressure drops or the pump fails, the pressure in the water line can fall below the pressure inside the spray system, creating a siphon that pulls pesticide back into the water supply. That scenario matches the idea of backflow, making it the correct choice. Other options describe different issues—evaporation is loss to air, adhesion is sticking to plants, and air entering during filling relates to air problems in the tank, not a reversal of flow back into the water supply. To prevent backflow, use backflow prevention devices or an air gap, and avoid cross-connections between the water supply and the spray system.