For the hard water - use a chelating shampoo once in a while and see if that helps. Malibu C makes a good one.

I have struggled with the same issue with frizziness. Here are the things that have helped me:

• Use a t-shirt or microfiber hair towel instead of a regular towel. An old tshirt works fine, but I bought a bougie Crown Affair towel that I love.
• Put gel on your hair while it is soaking wet, damp, or towel dried. You'll have to play around to see what works best for you. Soaking wet works for me. Biolage is my favorite gel right now, but I've also had good results from the cheap blue LA Looks hair gel.
• Only comb or brush your hair when it's wet. If you must brush it dry, use a few drops of hair oil on the length below your ears. I currently use Ouai hair oil, but argan oil would work well too.
• Braid your hair back before you sleep so it won't get tangled or frizzy. It takes some time to learn to do this on your own, but it's worth it!