Help with pH and TA

[Akronstax]

Working on converting a friend at work to BBB from shock and trichlor pucks. He brought me a sample of his water to test with my TF kit. Amazingly, his CYA was only around 50. But here is my question, when I test for pH, the color is so off the chart low it looks like it is almost non-existant. Then when I do the TA test, after I add the 5 drops of the 2nd solution where the water is supposed to turn green, it immediatly goes pink! So based on those results, should we attack the low pH or alkalinity first?
His pool is 13500 gallons. I am thinking of attacking TA first. The pool calculator says 20lbs of baking soda takes it from 0 to 100 - so I was going to recommend 10 lbs to start and then check the results. Can we try to raise the pH at the same time?

 

[JasonLion]

Those results suggest that the PH is around 4.5 and TA is zero. The best solution is to raise PH with borax. By the time you get the PH into range the TA should be fine. If you raise TA first the TA increase from raising PH will drive TA way too high.

Keep in mind that the Pool Calculator is not very precise for huge PH changes. So use much less than you think you need and do the PH increase in several steps, testing PH after each dose mixes in to see if you have gotten into range yet.

 

[Akronstax]

Thanks for clarification! Off to Walmart!