I probably will end up doing the partial drain (I should had been paying attention to this during the rainy season ). There will also be cost for replacing the salt and CYA of course.

We moved to this house 1 year ago, so I don't know the history. What causes CH to end up so high? Does the SWG contribute to this, or did the previous owner's maintenance cause this?

I do have to fight the pH several times a week with Muriatic acid, so I would like to raise the alkalinity if it is safe. It sounds like I have to get CH below 500 before I should raise the alk?

Thanks for the quick reply.