Thank you! I just tested a water sample from the hose and the CH was 125.
We just had to do a partial water replacement for high CYA levels a few weeks ago. Thanks to the support of this forum it was successful So there is a lot of "new" water in the pool (if that is important?!)
Assuming you’re Starting at 225ppm and your fill is 125, for every 10,000 gallons of fill water you add to the pool your CH level will roughly increase 85ppm so there’s no major worry about your fill water quickly raising your CH level out of control. Looking at this I personally would use Cal-Hypo for a week or two to increase your CH to at least 250, then kinda monitor it and maintain my CSI.