Falcon unstained E.T. drinkable water expansion tanks are to maintain harmless pressure in home water systems that utilize a rearward flow preventer or check valve. E.T tanks a 100 % butyl diaphragm and integrative liner to separated the system water from the tanks air precharge. The system connection a unstained steel sleeve to prevent corrosion making it even more certain. And, the tanks are with appliance quality paint which helps prevent external corrosion. On best of all this every E.T. tank is comprehensively and backed by Falcon 's 5 year constricted warranty. If this does n't all of the pressures that cause you to worry, nothing will.