What is the minimum vertical gap in an air gap required to prevent backflow?

The minimum vertical gap required for an air gap to effectively prevent backflow is twice the diameter of the discharge pipe. This standard is crucial for ensuring that any potential contamination from the downstream side of the system does not re-enter the potable water supply.

Having a gap that is twice the diameter of the pipe provides a significant buffer against the possibility of backpressure or backflow conditions that may arise due to sudden changes in pressure or flow direction. This greater distance enhances the safety of the water supply by ensuring that any backflow event cannot bridge the air gap, thus maintaining the integrity of the drinking water system.

Adhering to this standard is essential for water system operators and ensures compliance with health regulations meant to protect public health from contaminants.