Amtrol ST-12 Thermal Expansion Tank 4.4 Gallons 141N43 390748

The Amtrol ST-12 Thermal Expansion Tank 141N43 / 390748 is a 4.4-gallon in-line expansion vessel used in hot water systems to manage pressure changes caused by thermal expansion. It is installed in compatible closed-loop potable water heating setups, it accepts expanded water during temperature rise and stabilizes system pressure through an internal diaphragm separating air and water chambers. The unit is connected to the piping system via 3/4-inch threaded ports and is positioned inline near the water heater or hydronic circuit.