What Is a Cross Connection?
A cross connection is a direct or potential connection between any part of the public water supply system and a source of contamination or pollution. The most common form of cross connection is a garden hose, which is easily connected to the public water supply system and can be used to apply a variety of potentially dangerous substances, including chemicals and fertilizer. Other common cross connections include dishwashers, toilets, pressure washers, boilers, pools, and lawn sprinkler systems.
How Does Contamination Occur?
Water normally flows in one direction, from the public water system through the customer’s cold or hot water plumbing system to a faucet or other plumbing fixture. Under certain conditions, water can flow in the reverse direction.
This is known as backflow, and it occurs when back-siphonage or backpressure is created in a water line.
Backpressure may be created when a source of pressure, such as a pump, boiler, or other building creates a pressure greater than that supplied from the water distribution system; this may force water to reverse direction.
Back-siphonage may occur when there is a drop in the supply pressure of the water distribution system. This can be caused by a water line break, water main repair, or during a rapid withdrawal of water from a fire hydrant. This creates a vacuum, which may pull or siphon contaminants or pollutants into the drinking water supply.