From the beginning of TFP, TA has always been the least understood parameter for which we test. Lucky for us, it is also likely the least critical. Here are some random thoughts about TA....
1. The TA suggestions in the TF_100 test kit are what was established years ago and gradually, thye thinking on TFP has evolved towards lower vlues.
2. The TA guidelines for the TF-100 will likely be lowered in the next reprint. There is no rush to do that because the 80-120 suggestion in the kit is fine.....no harm done.
3. The belief on TFP has been that TA lower than 80 could cause your pH to easily swing wildly......experience teaches us that is not the case.
4. Many members on this forum routinely keep TA in the 50-70 range permanently with nothing but good results.
5. Keeping TA in that low range slows the natural pH rise in most pools and that is a good thing.
6. Other pools maintain TA's in the 100-120 area with no detrimental affect.
7. Many members deal with fill water that test TA in the 200+ range. Again, that seems to cause no long term harm and the TA immediately starts downward as outgassing in the pool water takes place.
8. I have always been just a little wary of the multiple suggestions we make for TA in pools with different surfaces (vinyl, plaster,fibergalss). They are certainly valid suggestions but I have always considered them as micro-managing. That's not what TFP wants....we want folks to go swimming and enjoy their pools.
8. So what will the suggestions for TA ranges be? I don't know for certain. We continue to digest all the info submitted on this forum and make an attempt at consensus based on that input. The guidelines in TFP pool school are the most up to date. I would follow those.