The Resideo BP900 Backflow Preventer W/Atmospheric Vent is a compact safety device designed to protect potable water systems in HVAC and plumbing applications. Commonly used in boiler feed lines and hydronic heating systems, it prevents contaminated water from flowing back into the clean supply. It operates using dual check valves and an atmospheric vent that opens under backflow or siphon conditions, releasing pressure and blocking reverse flow. This ensures system safety, maintains water quality, supports efficient operation, and reduces risk of contamination in residential and light commercial HVAC systems.