Current readings
CYA = 35
FC = 2.5 (I added a jug of bleach already and brought it up to 6.5)
TA = 50
CH = 40
PH = 7.2
Current Salt = <200
Current Borate = 0
Pool Volume
Based on rough measurements, I calculated the volume to be ~30k gallons. However, the addition of bleach per Pool Math values for 30k gallons has increased the resulting FC by a greater number than it says it should. By using the pool volume as the unknown variable and the volume of bleach and resulting FC increase, Pool Math is telling me that the pool volume is 20k and 22k gallons on two separate trials. I added 6 bags of solar salt and will do the same reverse calculation to see if it also indicates ~20-25k gallons.
TA and PH
I want to add the boric acid, which will lower my PH by ~0.3. I was going to bring TA up to 65 (I've read that the target should be between 60-90, but you should target the low end when adding Borates - so I chose 65. So I need 77 oz. of baking soda (assuming the 22k gallons described above). According to Pool Math, this will only raise my PH by 0.03... which is insufficient for the low PH and the additional drop that will occur when the boric acid is added... so I need to use the borax to help jump the PH without bringing the TA too high.
CH
I've read a variety of advice regarding recommended CH levels. I think Pool School says anything <300... but strewn throughout other postings are various other recommendations on level (even for vinyl pools). Based on everything that I read yesterday, I was planning to target 200.
My Question:
So, the main thing I'm trying to figure out is... are there chemical interactions that require things to be added in a specific order or separated by a certain amount of time? This is not really just a question for this addition, but for future adjustments both in my hot tub and in my pool.
For instance, last night when I got out of the hot tub and tested levels, it also needed PH and TA to increase along with a splash of bleach. I'm not sure if I can add Borax, Baking Soda, and Bleach all simultaneously or not. Doing so would save some time, but will it cause a problem? So last night I added the bleach, waited a while, then added the borax and baking soda.