I boil water and put it in old seltzer water bottles, and I wash my hair with it. My hair feels differently when I use the boiled water versus tap water (I'm in NYC, btw.). I also use porosity control at every wash.
I definitely notice a difference when using hard water in other areas (eg. Trinidad). When I wash my hair over there, porosity control and chelating shampoo is not optional. I also use Aphogee 2-minute over there because the product claims to displace mineral deposits from hard water. If I don't use hard water products for my hair when I'm over there, my hair feels like sandpaper.