What is the minimum air gap needed when filling tankers from a public water system?

The correct answer is based on the principle of backflow prevention to ensure that contaminants do not enter the public water supply during tanker filling operations. The minimum air gap required is crucial in establishing a physical barrier between the supply line and the tanker.

When filling tankers from a public water system, maintaining an air gap of at least two times the diameter of the inlet pipe is recommended. This distance reduces the risk of siphoning, where water from the tanker could potentially flow back into the water supply if the tanker were to experience a change in pressure or backflow conditions. By adhering to this minimum air gap requirement, operators significantly enhance the safety of the water distribution system, thereby protecting public health and maintaining the integrity of potable water sources.