Surely soap lathers better in soft water?
In Essex we have hard water, but throughout much of the county kettles don't properly fur up but have what is known as "egg-shell hardness". It's down to the wide shallow reservoirs we have, and the presence of enormous quantities of blue-green algae, all photosynthesising like buggery, and the chemical effect they have on the calcium salts. 'Twas my brother who told me this. He was a water company chemist for 42 years so it
must be true.
We have a water softener which was installed at the same time as our solar panel: solar panels fur up very quickly. We have one tap, the cold tap in the kitchen, which gives unsoftened water. I tend to wash my hands under the kitchen hot tap and rinse them under the cold tap. Softened water doesn't react with the soap so leaves a slimy film on your hands which takes ages to get rid of. The hardness in the cold tap gets rid of it straight away.
The softest water I know of is that in East Manchester. Mrs Wow's mother has a dark stain on her bath, which is a result of the water having come form a reservoir which collects from peat hills, or so I've been told..