Kara
You probably only have a 40 gal water heater now. Add another one same size and pipe it in with a five valve series/parallel piping arrangement. This way you can run the tanks in series with the initial tank set 10 degrees lower than the second tank. When one tank or the other goes out you simply shut off the appropriate valves and you can still use either of the two tanks, for the price of three valves…..Lou
