What are the two main types of backflow?

The two main types of backflow are backpressure and backsiphonage, which are essential concepts in understanding how water can flow in the opposite direction within a plumbing system, potentially leading to contamination of the potable water supply.

Backpressure occurs when the pressure in the non-potable system is greater than that in the potable supply. This can happen, for example, in situations where pumps or other mechanisms increase the pressure in a system connected to drinking water. If the pressure difference allows for backflow, harmful substances from the non-potable side can enter the potable side, creating a health hazard.

On the other hand, backsiphonage occurs when there is a negative pressure (or vacuum) created in the supply line, often due to a sudden drop in pressure or a break in the water main. This negative pressure can draw contaminated water into the clean water supply, further demonstrating the need for backflow prevention measures in plumbing systems.

Understanding these two types of backflow is crucial for ensuring public health and safety, as both can lead to the introduction of pollutants into drinking water systems if not properly managed.