BullFrogSpasMN said:
There's no chemical that will effectively lower calcium, you'll need access to a soft water source via a home water softener or a portable water softener like this:
https://hottubstore.com/product/caldera-on-the-go-portable-water-softener/
The water in my store is very hard so I use the portable softener when I fill my tubs and usually do a 50/50 hard/soft mix to get around a 125-150 ppm level.
Today I tested the TA and Ph of the water from my tap. TA was 370 and PH was 7.8. In my small town, most people use water softeners, mine died maybe ten years ago. ≈5 years ago, I bought a preowned, but never hooked up salt based soft water set up and about 4 bags of salt, but never got around to hooking it up. Being in the basement, it is out of sight out of mind. Back then I had even made plans to install whole house filters as too. I know those notes are buried somewhere. LOL So NOW I have a reason to put 'install water softener back on my to-do list.' It certainly won't happen for the first fill of the new tub! To bring down TA hopefully to 50-70 ppm, do you think the process of: 1) adding acid to decrease PH; 2) run aeration to increase PH; 3) retest TA... Repeat steps 1 thru 3 until I get TA to 50-70 ppm is doable within a reasonable amount of repeating this process?
I am in the office coffee business and have used 12" long Omnipure inline "softening" cartridges 1/4" in/out .5 GPM flow to reduce scale for coffee brewers. Do you think this dinky 12" 1/4" in/out filter which would theoretically add 200 gallons in ≈ 7 hours at it's spec'd 1/2 GPM from the tiny 1/4" in/out would be worth trying? I guess I could adapt it to my hose, start the .5 GPM flow into the tub, test the CH after about 30 minutes, then again 2 hours later to see if it is still delivering low CH water from the hose into the tub. Actually, it would be an interesting experiment to see its performance over 'X' gallons of water to know how well it is protecting my coffee equipment. Nothing to lose with the experiment, and maybe I'll get enough soft water to get a reasonable TA & PH, who knows.
You like to get 125 -150 ppm CH or TA?