"Cross-connection" or "cross-connected" as used in these regulations means any real or potential connection between any part of a public water system or other water system supplying potable water to members of the public and any auxiliary water supply or any source or system containing water or any substance that is not or cannot be approved as safe, wholesome, and potable for human consumption.
Three things must happen in order for a backflow incident to occur:
- An actual or potential cross-connection,
- A non-potable water source is present,
- Backpressure or a vacuum created within the plumbing.