Calcium in our pool reached our high threshold point earlier this month and we had reverse osmosis service performed to bring it down. And, yes, it brought nearly everything else down as well.
PH dropped to 6.8, TA dropped from 120->50, Borates went to almost zero, salt to 800, CYA to under 10, calcium to slightly under 100. Luckily, I had planned ahead and had replacement supplies on hand.
The RO service took about 17hrs and afterwards our CSI was briefly about -1.6. I got the borates in rather quickly to raise TA and PH, and then brought down CSI back into the -0.35 to -0.50 range over about 36hrs. Salt is back to 3400 and all appears to be running fine. The pool has stayed in the low CSI range for the last week - I was hoping warmer weather would help get it back above -0.30 but it may take another week or two to know if we get sustained higher temps. Due to our intellichem, the highest sustained PH I can keep is ~7.65.
Should I just wait or add a small amount of calcium to the pool water now, or how long can I reasonably wait with CSI this low? We have a pebble sheen finish that we try to be careful of. CH is currently 125 and I can see bringing it up to 150-160. Normally, CH increases by 10 pts during each winter month, and 15-30 pts during summer months.