How does NFPA 20 address backflow prevention?

• A. By mandating backflow prevention devices on all discharge lines regardless of demand.
• B. By eliminating any backpressure in the system through automatic relief valves.
• C. By prohibiting any connection to the public water supply.
• D. By requiring proper interface with water supply and appropriate piping design to maintain system integrity.

Answer: (C)

Backflow prevention in NFPA 20 is about how the fire protection water supply is tied into the public water system and how the piping is arranged to keep water from flowing backward into the supply. The standard requires a proper interface with the water supply and sound piping design to maintain system integrity, so that any pressure changes from the fire pump don’t create a path for potentially contaminated water to enter the potable supply. Where the AHJ or local water authority requires it, backflow prevention devices (such as check valves or backflow preventers) are installed at that interface to stop reverse flow.

It isn’t about putting backflow devices on every discharge line, and it isn’t about eliminating backpressure with automatic relief valves. It also doesn’t forbid connecting to the public water supply; instead, it governs how that connection is made and protected to prevent contamination.