We are on a well (rural area). The water is so hard here that when the house was built, they needed both a water softener and an iron filter to treat it.

I had an issue this winter with my septic system freezing up and in order to prevent an overflow before the tank could be pumped, I was told to put the treatment system on bypass (water softener cycles dump a lot of waste water down the drain). Even with the hard well water going through the dishwasher, it never failed to clean the dishes properly. This dishwasher is 22 years old.