Strange issue with Alkalinity and pH

[JimK]

If you really want to attack the TA issue, add baking soda in small quantities until you reach your goal or pH stabilizes. It will raise your pH some, so I still recommend lowering the pH first.

Jim has an interesting idea. When you get your pH and TA stable, adding borates has many benefits. The process of adding them is a roller coaster ride that swings your pH high with borax and low with MA, so I would recommend waiting for now.
Here is a link to the process: http://www.poolforum.com/pf2/showthr...stant-to-Algae
If you decide to go for it, test part way through. I found that I reached 50ppm about half way through the recommended dosage.

If you use boric acid (I buy it online) instead of borax, you don't have to add acid. Boric acid will lower pH a little, but I've not found this to be an issue for me.

See our last posts, but also: I reread your OP and I think your question was about why they recommended 80-100 TA. Jim can correct me if I'm wrong since I know only a little about SWGs. I believe the SWG system causes a certain amount of aeration/out-gassing which lowers TA a bit over time.

I've not noticed an impact on TA running my SWCG. I wonder if the boric acid in the pool has a stabilizing effect here as well?