Re the On the Go water softener.
Those that have met me will remember that I wear my hair long and in a pony tail, Reason: I am allergic to color and perms, the last time I had both I had rod burns that bled (EWWWWWWWWWWWWWWWW) and took weeks to heal. SO, no more coloring and no more perms. SOOO, I wear it long, grow it for 2 years, and then cut off and give to Locks of Love.
The purpose of that long descriptive paragraph is to explain ONE of the reasons I value the water softener so much. I don't want my hair damaged, do not dry it with a hair dryer unless it is so cold out that I have to.
(I also have yorkies, with show coats, aka: LONG HAIR)
When we are in places with hard water, and in the RGV was really the worst, I would wash my hair on Monday AM, Tuesday AM when I would try to comb it out it would feel like I was brushing concrete and I would have a sink full of hair, broken hair.
Same with dogs, when I would try to spiffy them up in between bathes I would end up with handfuls of hair.
So, we got the On the Go. No more broken hair, and even Al can feel the diffference of the soft water. He fought me a bit on this purchase, but first shower with it, he was a convinced soul!
OKKKK, for questions about where we place it, we have older Tana, it does not have the convenience center. We place the softener inline with hoses from camp hookup to Tana's inlet. It sets on the ground.
I believe that Al hooks up a duel type water filter first, then the On the Go, then into Tana.
We leave it sit out beside the rig, and don't even lock it up. Usually we only use it while we are in the RGV for 3 months.
As far as drinking water, the fur kids are on distilled water, per orders of the vet. We use same for our coffee and tea. We use WalleyWorld bottled water, the 20 ounce bottles, with minerals added for general water drinking. I am unable for a variety of health reasons to drink ANY water other than these two kinds. I also do not drink fountain sodas/pop, as they are made with local waters.
As far as the Calgon, if you read the site(s) referred to above you will read that the reason to use Calgon when doing laundry is:
"removing hard water minerals that trap dirt into fabric fibers. It also helps prevent detergent build-up and soap scum that can cause clothing to appear dull and faded."
In our gray, galley and black tanks, we are interested preventing soap scum and build up, and removing hard water minerals that mess up EVERYTHING!
That is why we use the laundry version of Calgon, and nothing else. That said, I am unfamiliar with Calgon for spas. I personally would not use the Calgon for baths, even tho it might "take me away".