We have super hard water too, it's not great My hair is very thin and very fine (boo), so by the second day I have lost ALL of the volume... from the ears up, where I want it. I only wash my hair twice as week-ish, and it's quite long right now.
On fresh wash day, I use Bumble & Bumble’s curl creme for fine hair which is the only curl creme I've found that's light enough for my thin/fine curls while they're as long as they are now (when short I can use a denser creme). Use a good dollop when wet and focus on the ends, scrunch and let air dry. Easy peasy!
But on the second day, I have to do a lot more work. I use a small amount of the creme and blend with water and gently work into the bottom half of my hair and use the excess along the top and inside near the scalp. More scunching, lots of it. I also have to tease the hair up at the back of my head because I have a head-sized cowlick back there -_-
On the third day+, I usually also have to use some dry shampoo along the scalp if I plan to wear my hair down so I start with that then do the curl creme only on the bottom half of my hair (and even more crown teasing). But usually I put it up by this day, either in a pony tail, a fanned bun, or half-up. My curls tend to behave themselves well enough with the curl creme, but nearly all of the work involved is me trying to get the volume back. If my hair was thicker it wouldn't be a problem.
