My water is hard. I will buy a gallon of filtered water at store for washing. Are there benefits for using Distilled or deionized water for washing unit?

I've heard others say they've benefited from fitting a water softener, so it must help.

ANYTHING that reduces harsh chemicals & treatment of the hair will all help.
Its just a question of how far do you go?

I spent years dwelling on my hair and what it looked like.
For me, the idea of wearing was so that I could forget about it more and get on with other things in life.
I feel if I followed every precaution & piece of advice offered, I'd be a slave to hair again.
Now I just stick to being sensible about what I use on the hair and careful about the products I choose and the amounts I use them in.
The number one hair killer (in my opinion) is heat, from too hot water, a hairdryer or the sun.
Just avoiding those has extended the life of my pieces.
Beyond that, I try and keep it as simple as possible.

That makes sense. I live where the water is extremely hard. Even with a water softener it leaves a white residue in sink after time. I at least need purified water. It will cost about 75 cents a gallon either way. Just not sure which is best. I hear distilled may be best choice. Just wanting more feedback