I've been only using distilled water - I keep gallons of it because we have extremely hard water here in central Texas.
I wished I would have gotten the water softener option added to my home when I had it built back in 2000 - worst cost cutting decision I ever made. I am pretty sure the amount of water parts and
CLR I have had to buy would have paid for that option 10 times over by now. Though the
CLR has come in handy cleaning out these steam engines I been working on.