What is the 'Critical Level' in relation to a potable water supply?

The 'Critical Level' in relation to a potable water supply refers to the minimum elevation that backflow prevention devices must be installed above the flood level. This concept is crucial in plumbing as it helps to protect the potable water supply from contamination due to backflow, which can occur when there is a change in pressure that causes water to flow in the opposite direction. By maintaining the critical level above the potential flood elevation, the risk of backflow entering the clean water supply is significantly reduced.

Properly placing backflow prevention devices at or above this critical level ensures that any floodwaters do not come into contact with the potable water system, thus maintaining the safety and integrity of drinking water. Understanding this concept is essential for complying with plumbing codes and ensuring public health and safety within plumbing installations.