Back flow is defined as: “The undesirable reversal of flow of water or mixtures of water and other liquids, gases or other substances into the drinking water system. Occurs due to a pressure differential between two points within a continuous fluid system.” Back flow can occur where there is a cross connection between the public drinking water system and other pipes (like a sprinkler system), or other source of water, industrial fluid, gas or other substance, that can flow into the drinking water system as a result of pressure changes. (As a simple illustration, think of a siphon hose.)
The dangers of back flow is such that the State Division of Drinking Water has approved the following Rule to apply to Public Water Systems:
Rule 309-105-12: “[A] water supplier shall not allow a connection to his system which may jeopardize its quality and integrity. Cross connections are not allowed unless controlled by an approved and properly operating backflow assembly.
