Jason-

My pH has been drifting up as well. Here are my numbers:
FC 3-5
pH 7.8
TA 80 (it was at 70- I mistakenly raised it with Baking soda thinking since TA buffers pH, more would be better)
CH 270
CYA 35
Borates 50
Salt 2090 (no SWG)
temp 82 degrees

Even though Pool School recommends TA from 70-90+, it sounds like you are recommending lowering TA to 60 and possibly even as low as 40 to try to stabilize pH drift. Is that correct?

My question, then, is how to effectively lower TA when I have no aerating features and no eyeballs on my returns. One of the 3 returns barely ripples the water about 6' away from the wall. Will lowering pH to 7.2 and letting it drift back up naturally bring the TA down? Or do I need to find some way to aerate the water?

The simplest thing to do is to lower the PH to 7.2 any time it gets up to 7.8 and stop raising TA. Over time that will bring your TA down.

Thanks, Jason.

So would TA of 40-60 be OK if that's what stabilizes my pH?

And when attempting to lower TA, is aeration only necessary to bring pH back up if the pH doesn't come up on its own? Or is it somehow better to raise pH more quickly with aeration?

Yes, TA as low as 40 is fine (because you have borates in the water, otherwise you would want TA a little higher).

Aeration can often speed up the process of lowering TA, by getting the PH to come up more quickly so you can add more acid. As long as the PH is coming up on it's own there is no need to aerate.

OK, so now my TA is down to 60 and CH is up to 340. PH is still drifting up. I see on the pool calculator that if I bring my TA down to 40 and pH to 7.6 that I'm getting dangerously close to a CSI of -0.6. (At 7.5, it would be less than -0.6) Would you recommend raising CH even higher (like 500)?

How old is the pool surface? Is the PH drift extreme or does it creep up over a week or so? Have you tried to see how far it will drift up. Some pools stop drifting at 7.7 or so.

I'm guessing the pool is at least 6 years old. The pH will typically go from 7.5 to 8.0 in a little less than a week. It was much more stable before I added Borax to get the borate level up to 50.

Any ideas?

So TA is now 50 and pH went from 7.3 to 8.0 in 2 weeks- an improvement, but still would like it to be more stable. If I take TA down to 40, how high would you recommend I raise CH to keep CSI over -0.6?