What is the best means to prevent contamination of drinking water supply with plant water?

The best means to prevent contamination of a drinking water supply with plant water is to implement an air gap. An air gap is a physical separation between the drinking water supply and any potential source of contamination. This gap effectively prevents backflow, which is the unintended reversal of flow that could occur if there were a drop in pressure within the water supply system.

By maintaining this gap, there is no direct pathway for contaminants from plant water or other sources to enter the drinking water supply, ensuring the safety and integrity of the potable water. Air gaps are commonly used in plumbing systems to protect against various hazards, including biological contaminants.

Other methods, while useful in certain situations, do not provide the same level of protection. For instance, check valves are designed to prevent backflow but can fail or become stuck, leading to potential contamination. Pneumatic control valves are typically used for controlling flow and pressure within a system but do not inherently provide backflow prevention. Gravity drains, on the other hand, allow for drainage but may not effectively prevent contamination if not properly designed.

Overall, the air gap stands out as the most reliable method for maintaining the quality of drinking water and safeguarding it from contamination.