Ben, Thanks so much for your reply.

The pool and spa are at the same level, divided by a low tile wall with a spillway. I try to keep the water level about an inch below the spillway and the flow over the wall is low, with no obvious bubbles. I can try to fine tune the mixing valves to reduce the flow. I haven't experimented with sending most of the return directly to the pool. There is a makeup line from the pool return to the spa, and that may be enough. That's probably what I'll do when I get the cover on.

If I understand correctly, you're saying that I need to get the TA down to 60 ppm using the aeration method. I have a blower on the spa, which I never use, and that should do the trick. How long do I wait between acid additions as I creep down to 6.8? Using the acid demand test in the K2006, I have an excellent idea of acid volumes for my pool to make small (.2 to .4) changes in Ph, but I'll follow your standard advice to use multiple doses for this big change. Does the borax act as a Ph buffer?

Thanks again.

John