Factors That Create a Cross-Connection Incident 2

The Link – In this diagram, a cross-connection exists because there is a connection between the potable water system and the non-potable system. There is a gate valve separating the two but is not considered approved backflow protection. In this situation, the potable water system pressure is greater than the pressure in the non-potable water system. As long as this situation exists, the cross-connection is not a hazard because there no resultant forces toward the potable water system. However, pressure in the water distribution system and domestic water system changes resulting in the pressure of one exceed the pressure of the other and may have flow from one system to the other because of the pressure differentials.

The Link and Resultant Force – In this diagram the cross-connection between the potable a non-potable water system is separated by a valve. In the previous diagram, the potable water source pressure was greater than the pressure of the non-potable source. However, a resultant force is now toward the potable water system creating a backflow situation. It can be backpressure backflow or back-siphon backflow.  In a backpressure backflow situation, the non-potable water pressure is greater than the potable water pressure and non-potable water in entering the potable water supply system. In a backsiphonage backflow situation the non-potable water system is in a siphon state and the potable water is in a negative or sub-atmospheric state.

The Water Quality – The contaminant could be body fluids from mortuary or the pollutant could be wine from a winery. All three factors are occurring at the same time; therefore, a cross-connection incident is occurring.