To prevent back-siphoning when loading or cleaning a pesticide sprayer, which precaution is recommended?

• A. Use a containment dike to contain spills, rinsates, and runoff water
• B. Maintain an air gap between end of hose and liquid in tank to prevent back-siphoning
• C. Open the end valve to vent pressure
• D. Drip rinse water onto ground

Answer: (B)

Preventing back-siphoning is about breaking the path that could pull liquid back toward the source when loading or cleaning the sprayer. Keeping an air gap between the end of the hose and the liquid in the tank does exactly that: it creates a break in the liquid column so a siphon cannot form if pressure changes or if the system is shut off. With an air gap, the hose end isn’t submerged, so contaminated rinsates or spray contents cannot be drawn back into the supply or source beyond the gap. This simple measure protects drinking water and avoids contamination of the applicator or environment. Other options don’t address the siphon mechanism: containment dikes deal with spills on the ground, venting the hose can release contents, and dripping rinse water onto the ground spreads contamination rather than preventing backflow.