EXPT2 Falcon Potable Water Expansion Tank for 50-Gallon Water Heaters The nagging worry of eliminating system pressure has all but been eliminated. Falcon Stainless E.T. potable water expansion tanks are designed to maintain safe pressure in domestic water systems that utilize a back flow preventer or check valve.E.T tanks feature a 100% butyl diaphragm and plastic liner to separate the system water from the tanks air precharge.The system connection has a stainless steel sleeve to prevent corrosion making it even more reliable. And, the tanks are finished with appliance quality paint which helps prevent external corrosion. On top of all this every E.T. tank is comprehensively tested and backed by Falcon’s 5 year limited warranty. Tank: 16 gauge cold rolled steelFinish: Appliance quality paint for indoor or outdoor installationWater chamber: 100% butyl rubber, lined with polypropyleneConnection: Stainless SteelTesting: High pressure, seam weld, helium, final precharge checkAir valve: Brass valve with o-ring sealWarranty: 5 year limited