In a cross-connection scenario, which equipment has the greatest potential to contaminate the water?

• A. A pesticide mixing tank
• B. A non-contact storage tank
• C. A sedimentation basin
• D. A potable water storage tank

Answer: (A)

When assessing cross-connections, the concern is which source could introduce a harmful contaminant into the drinking water if backflow occurs. A pesticide mixing tank represents the greatest risk because it contains concentrated pesticides and other toxic chemicals. If backflow happens, these hazardous substances can be drawn into the distribution system and pose immediate health risks to consumers. The other options involve equipment that either does not introduce hazardous substances (a non-contact storage tank is designed to stay separate from the water, reducing the chance of contamination) or stores treated or potable water, which is not itself a contaminant source. Thus, the pesticide mixing tank is the highest-risk source in a cross-connection scenario.