For use in closed-loop, non-potable water heating systems4.7-gallon capacityDurable steel tank60 psi maximum working pressureUse the Watts series ETX water expansion tank in tandem with your hot water heater to absorb increased water volume resulting from hot water boiler heating and keep system pressure below the relief setting. Use in closed-loop, non potable water heating systems. Durable steel tank with 60 psi maximum working pressure.