[editor-surveyor]

>> “It was wonderful until the hard water destroyed the holding tank.” <<

.
Very similar to my experience with solar water heating. The freeze valves would stick open first, then later on the tanks went.

Soft water errodes the tanks (dissolves the copper and the steel), and hard water clogs and corrodes them

[Myrddin]

I left the tanks on the roof until it was time for a roof job. At that point, they were permanently removed. I sold the house a couple years later.