The Xylem-Hoffman Specialty 401485 3/4" Water Vent 150 PSI Max 78 is an automatic float-operated air vent designed for hydronic heating and cooling systems. Rated for up to 150 PSI, it removes trapped air from water lines to maintain efficient circulation and prevent air-related issues. As air accumulates, the internal float mechanism lowers to release it and reseals once cleared. Com... https://www.partshnc.com/78-water-vent-34-150-max