The difference between “soft water” and hard water has been beaten to death for washing clothes and drinking but not enough emphasis is put on how difficult it makes cleaning.
With distilled water at 89 cents a gallon even cleaning companies such as us don’t bother with tap water.
Hard water contains “extra stuff” that creates film, streaks, and even contributes to oxidation (rust) on surfaces overtime such as stainless steel and porcelain:
The extra stuff listed above settles on surfaces after cleaning and contributes dramatically to grout in shower walls/floors and most floors degrading and looking dull and dark.
Most modern cleaning products contain chelating agents which are specifically in place to bind with metal ions in hard water and free up the surfactants (detergent in cleaning product) to do it’s job and clean.
The problem is that even with chelating agents hard water degrades the performance of surfactants (detergents) in cleaning products by about 50% typically.
When using distilled water you will find that magically you will have to use about half the cleaning product and get 2x the results!