How many times the effective opening of the water supply outlet piping must the vertical distance of an air gap separation be?

In backflow prevention, the air gap serves as a crucial method for separating potable water supplies from contaminated sources. The standard for determining the vertical distance of an air gap separation is that it must be at least two times the effective opening of the water supply outlet piping.

This means that if the outlet has a specific diameter or opening size, the air gap must exceed this size by a factor of two in vertical distance. This safety measure is in place to ensure that any potential backflow that may occur does not contaminate the potable water supply.

When using a different multiplier, such as three, four, or five times, it would create unnecessary requirements that are more stringent than necessary for maintaining an effective air gap. Therefore, the standard of two times offers a balanced approach to safety and practicality in backflow prevention measures, making it the correct choice.