What is Cross-Connection?
Cross-connections exist whenever the drinking water system is or could be connected to any non-potable source (plumbing fixture or equipment used in any plumbing system). Pollutants or contaminants can enter the safe drinking water system through uncontrolled cross-connection when backflow occurs.
Where are Cross-Connections Found?
Cross-connections are found in all plumbing systems. It is important that each cross-connection be identified and evaluated as to the type of back-flow protection required to protect the drinking water supply. Some plumbing fixtures have built-in back-flow protection in the form of a physical air gap. However, most cross connections will need to be controlled through the installation of an approved mechanical back-flow prevention device or assembly. Some common cross-connections found in plumbing and water systems include:
-Wash basins & service sinks
-Irrigation sprinkler systems
-Auxiliary water supplies
-Swimming pools/hot tubs
-Photo developing equipment
-Solar heat systems
-Fire sprinkler systems
-Water re-circulating systems
What is Back-Flow?
Backflow is the unwanted flow of non-potable substances back into the consumer’s plumbing system and/or public water system (i.e., drinking water).
There are two types of backflow conditions:
Back siphonage - occurs when the supply pressure at the water connection point decreases below the pressure on the consumer's side. This could be caused by a water main break, water system repairs or large fire demand.
Back pressure - occurs when the consumer-side pressure overcomes the normal supply pressure. This could be caused by the operation of a boiler or a separate booster pump system connected to the consumer’s piping.