The Xylem-Bell & Gossett 110199LF Dual Valve 8 is a combination pressure-reducing and relief valve designed for dependable pressure control in hydronic HVAC systems. It automatically reduces incoming water pressure to a preset 12 PSI for proper system filling while providing a 30 PSI relief function to protect against over-pressurization. https://www.partshnc.com/110199lf-xylem-bell-gossett-8dual-vlv12-12rduc30rel