A cross-connection is any faulty plumbing connection to a potable water supply system through which potable (drinking) water is supplied to a service outlet and through which contaminants unfit for human consumption can enter the potable water lines by back pressure or back siphonage backflow.


During a backflow event, these contaminants could be drawn or pushed back into the potable water distribution system. The pollution from a cross-connection can cause the water to become aesthetically unappealing, creating problems such as strange tastes, odors, and/or colors. A cross-connection can also allow a contaminant to enter the potable water lines, causing illness or death to those who consume contaminated water.

How Cross-Connections Occur

A cross-connection happens when a contaminant or pollutant source is plumbed into a potable water line, or a contaminant or pollutant enters a water line through a break or opening.

Additional Information

For more information on cross-connections, please visit Examples and Repairing a Cross-Connection.