A cross-connection is present when there is a possibility that potable water could mix with non-potable water. Cross connections can easily happen in any home and can pose potential health dangers to inhabitants. There are a number of documented cases where cross-connections are said to have caused people serious illness, injury, and in extreme cases, death. This course will provide an in-depth look into plumbing cross connections, plumbing systems, and why cross connections should be inspected or determined. In addition, this course will review the processes of inspecting the plumbing piping, sanitary piping, and vent system, and will offer some facts that pertain to plumbing systems and cross connections regarding residential construction.