The Great Tetraborate Experiment!

[chem geek]

With the higher pH and TA, this increases the saturation index. The higher salt level and lower CH (235) decrease it somewhat. The net result I now get is -0.35 which is better than the -0.47 I was seeing before. The actual carbonate alkalinity is 57.0. If I remove the Borates and keep the measured TA the same, then I get a carbonate alkalinity of 64.4 so though the Borates do not have a large effect, they do have some effect on alkalinity and therefore any "adjustment" calculation.

I'm glad to hear that you resolved your rising pH issue by lowering the TA only to 90 instead of 70, especially with the high CYA levels needed for the SWG. That makes this "lower TA" recommendation more reasonable for people combating rising pH without having to adjust too much of the other parameters.

If you increased your CH to 300, the saturation index would be -0.21; increasing it to 400 would make the index -0.09. Of course, raising the pH by 0.1 raises the saturation index by the same amount and is another alternative. Since you're not seeing any problems, you could of course just keep things as they are. Raising the CH to 300 or 400 wouldn't be hard now that you've stabilized your pool with all its parameters tweaked the way you want them (i.e. borates, salt, CYA). Just FYI.

Richard