Which practice prevents back-siphoning of pesticide into the water supply?

• A. Installing a backflow preventer on the irrigation line
• B. Keeping an air gap or using anti-siphoning devices on garden hoses
• C. Replacing hoses after each use
• D. Relying on gravity to prevent siphoning

Answer: (B)

Back-siphonage happens when the water pressure in the supply line drops, allowing contaminated water—like pesticide solutions from a hose—to be drawn backward into the potable water system. An air gap or an anti-siphon device on a garden hose provides a break in the path to the water supply or vents the line to the atmosphere, so no suction can pull pesticide-laden water back into the supply. This simple, immediate barrier at the point of use is the most reliable way to prevent back-siphoning when pesticides are applied through hoses.

A backflow preventer on the irrigation line is also a protective measure, but it’s a broader system device that may not cover all hose-use scenarios and can require proper installation and maintenance. Replacing hoses after each use or relying on gravity don’t address the siphon mechanism and aren’t effective safety controls in this context.