JasonLion,
I certainly agree with you, despite having a pH controller and acid feeder, there were over the course of the 18 hours the pump was off fairly wide pH swings at that time. With that high a CH it is certainly probable in retrospect that this was the cause.
At present the pH hardly moves at all and only about 1 oz a day of acid is being remitted to the pool, hopefully those days are over.
The reason I tried the higher CH was to avoid putting as much baking soda as I use to. Also I wanted the pH at 7.4 or below to control iron staining but it seems that the now switched to Purple stuff from the Magenta stuff is keeping that in check. As there is no apparent scaling going on now I think that my staining and scaling issues may, I hope, be behind me.
With the higher present pH of 7.7 -7.8 I am using about 23 oz of Baking Soda every 3 to 4 days as the TA drops from 80 to 70 but the pH is hardly moving at all and hopefully scaling will not occur.
Is this drop of 10 ppm of TA in 3 to 4 days normal?
I do remember reading an article many years ago by the designer of pools for the Olympic Games (not an Olympic size pool designer which I am aware is completely different) where they mentioned that they preferred a pH of 8.0, which would probably mean a lower TA of 60. They felt that this caused less corrosion to both equipment and the pool itself. I wish I saved the article but I did not, if I find it again I will post a link. Pools built for the Olympics are I think tiled so there maybe differences in the approach. Also I am not sure if they lowered the pH for the games themselves. I do remember one other fact I found startling and that was the Chlorine levels for the actual games were very high in the pool itself and extremely high in the pre/post-dip shallow pool, presumably for sanitation purposes. As this article was read some years ago the philosophy may have changed.
I will stick with my present balance allowing the pH to go to 7.8, the CH to move down to 325, and the TA to move to 70.
But do you have any thoughts on this designers approach to pH?
Thank you for your help.