The answer to 'what is backflow preventer' is a device that prevents water from flowing backward into a home's plumbing system. Backflow preventers are critical for protecting the clean water supply from contamination. They are typically installed where the main water line enters a home, and they allow water to flow in only one direction - from the municipal water supply into the home's plumbing.
Backflow preventers come in different types, including atmospheric vacuum breakers, pressure vacuum breakers, and reduced pressure zone (RPZ) assemblies. The type used depends on the specific plumbing setup and potential hazards. Proper installation and regular testing are important to ensure the backflow preventer is working effectively.