The purpose of properly installing and testing an approved backflow device is to protect all of our customers from possible contamination.
Backflow means the undesirable reversal of flow of a liquid, gas, or suspended solid into the potable water supply; a backflow preventer is designed to keep this from happening. See the diagram below which shows one type of backflow preventer. There are several styles; this is just an example.
For more information about backflow prevention, visit the Spokane Regional Cross Connection Control Chapter website at http://www.src4.org/ed.htm.