Which method is appropriate to protect a potable water supply servicing a tank with a toxic solution?

To protect a potable water supply servicing a tank containing a toxic solution, creating an air gap is the most effective method. An air gap is a physical separation between the water supply and the tank, ensuring that any potential contaminated water cannot flow back into the potable water system. This method relies on gravity to maintain the separation, so even in the event of a backflow situation, contaminants cannot reach the drinkable water source.

In contrast, other methods such as a dual check, double check, or single check valve do not provide the same level of protection. These devices may reduce the risk of backflow but can fail under certain conditions, especially when there is a high degree of backpressure or other weaknesses in the system. Therefore, the air gap method remains the gold standard for safeguarding drinking water from hazardous substances.