What is considered the most effective method of cross-connection control?

A physical air gap is recognized as the most effective method of cross-connection control because it provides a clear, unobstructed separation between the water supply and any potential contaminants. This means there is no direct physical connection that could allow polluted water to flow back into the potable water system, thus safeguarding public health.

In practical terms, a physical air gap involves leaving a vertical space between the end of a water supply pipe and the surface of the receptacle it fills, such as a sink or tank. This gap ensures that even in situations of backflow, which can occur due to changes in water pressure or other system dynamics, contaminants cannot reach the clean water supply.

Other methods, while useful in controlling cross-connections, do not offer the same level of protection. For example, check valves can sometimes fail or become clogged, while vacuum breakers are less effective in certain situations. Pressure regulation, although important for system integrity, does not directly prevent backflow in the way that a physical air gap does.