A Cross Connection is created when any link or channel between piping, which carries potable drinking water and the piping or fixtures, which carry nonpotable water or other substances.
Nonprotected cross connections can cause contaminates to enter the drinking water system such as E. coli, Giardia, Cryptosporidium cyst and other Bacteria.
Cross connections are found in all plumbing systems. It is important that each cross connection be identified and evaluated as to the type of backflow protection required to protect the drinking water supply. Some plumbing fixtures have built in backflow protection in the form of a physical air gap. However, most cross connections will need to be controlled through the installation of and approved mechanical backflow prevention device of assembly. Some common cross connections found in plumbing and water systems include: