What is the minimum pressure allowed on a distribution system to prevent backflow and cross connection?

Maintaining a minimum pressure in a water distribution system is crucial for preventing backflow and cross-connections. The acceptable minimum pressure to achieve this is typically recognized as 20 PSI. When the pressure drops below this level, it can create a vacuum or negative pressure, allowing contaminants from non-potable sources to enter the potable water supply through backflow or cross-connections.

In practical terms, ensuring a minimum pressure of 20 PSI helps maintain the integrity of the public water supply and protects public health. Adequate pressure acts as a barrier against back siphonage, which can occur if there is a sudden drop in system pressure—potentially causing water to flow back from undesirable sources into the drinking water. Additionally, standards set by health and safety regulations usually align with this minimum requirement, emphasizing the importance of proper pressure management in distribution systems.