4.4 Gal Thermal Expansion Tank

4.4 Gallon, Thermal Expansion Water Heater Safety Tank, Steel Outer Shell, Polypropylene Lined Water Reservoir, Heavy Duty Butyl Diaphragm That Flexes, Leak Proof Precharged Air Chamber, Reduces Pressure Build Up & Harmful Pressure Spikes In Closed Water Systems, Temporarily Absorbs Expanded Water Overflow.