A primary cause of reversal flow of water in a piping system is:

The reversal of flow in a piping system is primarily associated with the loss of pressure. When there is a significant drop in pressure, it creates a condition known as backsiphonage, where water can flow in the opposite direction. This is particularly critical in systems where there are potential sources of contamination, as reversed flow can allow contaminants to enter the potable water supply.

Loss of pressure can occur due to several reasons, such as a breakage in the water main, excessive draw from fire hydrants, or other high-demand scenarios. In these situations, the negative pressure or vacuum may draw water from connected sources back towards the origin, causing contamination risks.

Understanding this principle is essential for backflow prevention professionals, as it highlights the importance of maintaining proper pressure in a piping system to ensure the safe and effective distribution of water. Implementing backflow prevention devices can help mitigate the risk of reversed flow and protect the integrity of the potable water supply.