Quote Originally Posted by Toybuilder View Post
I'll throw in my two cents for what it's worth.

From what I was told (by chem geek), your CSI should be between -0.3 and +0.3. I try to shoot for the middle of all the recommendations on that page. For your setup I would probably go with:

FC - 3 or 4
pH - 7.6
TA - 80
CH - 300
CYA - 40


Assuming no SWCG and with a temp of 65 your CSI would be -.11 which the calculator will tell you the water is balanced. If your water ever got up to 100, your CSI wold be +.19 which would still be balanced. Right now with the current numbers you've input, "Corrosion of plaster is likely". If you go the other way and your CSI is +.3 or greater "Scaling is possible".

I played with that calculator quite a bit to figure out what would be best for my spa and for the pool. Seems to be working out pretty well for me.

Figure out what works best for you and then try to hold those numbers.

Hope I didn't over step my boundaries. Good luck!
I would add to be careful not to go too low on the FC. 3 is at the lowest end recommended for your CYA; it leaves no room for error. I'd shoot for mid recommended range, so about 5ppm.